Defect detection method and defect detection device and defect observation device provided with same

ABSTRACT

The disclosed device, which, using an electron microscope or the like, minutely observes defects detected by an optical appearance-inspecting device or an optical defect-inspecting device, can reliably insert a defect to be observed into the field of an electron microscope or the like, and can be a device of a smaller scale. The electron microscope ( 5 ), which observes defects detected by an optical appearance-inspecting device or by an optical defect-inspecting device, has a configuration wherein an optimal microscope ( 14 ) that re-detects defects is incorporated, and a spatial filter and a distribution polarization element are inserted at the pupil plane when making dark-field observations using this optical microscope ( 14 ). The electron microscope ( 5 ), which observes defects detected by an optical appearance-inspecting device or an optical defect-inspecting device, has a configuration wherein an optimal microscope ( 14 ) that re-detects defects is incorporated, and a distribution filter is inserted at the pupil plane when making dark-field observations using this optical microscope ( 14 ).

TECHNICAL FIELD

The present invention relates to a defect detection method, a defectdetection device, and a defect observation device including the same forinspecting defects and the like on a surface of a bare wafer withoutsemiconductor patterns or a filmed wafer without semiconductor patternsor on a surface of a disk.

BACKGROUND ART

For example, in a production process of semiconductor devices, presenceof foreign matter or pattern defects such as a short-circuit and adisconnection (defects described hereinafter include foreign matter andpattern defects) on a semiconductor substrate (wafer) causes failuresincluding an insulation failure and a short-circuit in the wiring.Further, as the circuit pattern formed on a wafer becomes finer, a finerdefect also causes an insulation failure in a capacitor and destructionof a gate oxide film or the like. As for defects, matter appearing froma movable unit of a transporting device, matter generating from a humanbody, matter produced by a reaction of process gas in a process device,and matter beforehand mixed in agents and materials are mixed due tovarious causes and in various states. Hence, detecting a defect takingplace during the production process and determining the source of thedefect in a short period of time to thereby prevent defective productsare important to mass-product semiconductor devices.

Heretofore, as a method of ascertaining the cause of a defect, there hasbeen a method in which the position of the defect is first identified bya defect inspection device and the defect is precisely observed and/orclassified by use of a Scanning Electron Microscope (SEM) or the likeand is compared with a database, to thereby estimate the cause of thedefect.

Here, the defect inspection device is an optical defect inspectiondevice which emits light onto a surface of a semiconductor substrateusing a laser to conduct dark-field observation of scattered light fromthe defect to thereby identify the position of the defect, or an opticalappearance-inspection device or an SEM inspection device in which lightof a lamp or a laser or an electron beam is emitted to detect abright-field optical image of a semiconductor substrate and the image iscompared with reference information to thereby identify the position ofthe defect on the semiconductor substrate. Such observation methods havebeen disclosed in patent literature 1 or 2.

Additionally, as for the device to precisely observe a defect by an SEM,there have been respectively described in patent literature 3 to 5 amethod and a device in which by use of positional information of adefect on a sample detected by a second inspection device, the positionon the sample is detected by an optical microscope installed in the SEMdefect inspection device to correct the positional information of thedefect on the sample detected by the second inspection device and thenthe defect is precisely observed (reviewed) by the SEM defect inspectiondevice as well as an operation in which when the defect is observed bythe SEM defect inspection device, the height of the sample surface isoptically detected to be aligned with a focal position of the SEM.

CITATION LIST Patent Literature

-   Patent literature 1: JP-A-07-270144-   Patent literature 2: JP-A-2000-352697-   Patent literature 3: U.S. Pat. No. 6,407,373-   Patent literature 4: JP-A-2007-71803-   Patent literature 5: JP-A-2007-235023

SUMMARY OF INVENTION Technical Problem

When detecting a defect on a surface of a semiconductor substrate by useof an optical defect inspection device, in order to raise the throughputof the inspection, the laser beam for the dark-field illumination isemitted onto the surface of the semiconductor substrate with its spotsize enlarged to thereby scan the surface of the semiconductorsubstrate. Hence, the precision of positional coordinates obtained usingthe position of the laser beam spot to scan the surface of thesemiconductor substrate includes a large error component.

When it is desired to precisely observe a defect using an SEM based onthe positional information of the defect including such large errorcomponent, there may occur a situation in which the defect to beobserved is outside the visual field of the SEM which observes it with amagnification factor extremely larger than that of the optical defectinspection device. In such situation, to place the image of the defectto be viewed in the visual field of the SEM, the operator makes a searchfor the defect by moving the observation point in the visual field ofthe SEM; this takes a long period of time and causes the reduction inthe SEM observation throughput.

Therefore, it is an object of the present invention to provide a defectobservation device in which when precisely observing, by use of an SEM,a defect detected by an optical defect inspection device or an opticalappearance inspection device, it is possible to detect, with highsensitivity, a fine defect detected by the optical defect inspectiondevice or the optical appearance inspection device and to surely placethe defect in the visual field of the SEM, and it is possible to reducethe defect observation device in size.

Further, in the recent LSI production, due to finer circuit patternscorresponding to needs of high integration, the width of the wiringpatterns formed on a wafer is reduced. On the other hand, to secureconductivity of the wiring, the height of the wiring pattern isincreased.

In association therewith, it is desired in the optical defect inspectiondevice to reduce the size of the defect to be detected. In suchsituation, for the optical defect inspection device, it has beingdesired to enlarge the Numerical Aperture (NA) of the objective lens forinspection, and an optical super-resolution technique is underdevelopment; however, the NA value thus enlarged of the objective forinspection has arrived at the physical limit and it is hence anauthentic approach that the wavelength of the light to be used for theinspection is reduced to short wavelengths in the ranges of the UV lightand the Deep UV (DUV) light.

However, the LSI devices include memory products formed primarily usinga high-density repetitive pattern and logic products formed primarilyusing a non-repetitive pattern, and the patterns to be inspected arecomplicated and diversified in structure. Hence, it is difficult tosurely detect a defect (target defect) to be controlled at LSI deviceproduction. The target defects desired to be detected include, inaddition to foreign matter appearing during the respective productionprocesses and contour failures in circuit patterns after etching, a voidand a scratch in the CPM process. Moreover, there also exists a shortcircuit (to be also called a bridge) between wiring patterns in the gatewiring and the metallic wiring unit of aluminum or the like.Particularly, the short circuit between wiring patterns is lower in theheight than the wiring patterns in many cases, which hence leads to aproblem of difficulty in the detection.

Also, in LSI devices including multilayer wiring, since the targetdefects become finer and the underlay patterns in places where defectstake place are also diversified, it is more difficult to detect thedefects. Particularly, in the process in which the transparent film(indicating here transparent with respect to lighting wavelength) of aninsulation film or the like is exposed to the upper-most surface, thenon-uniformity in the intensity of interference light due to quite asmall difference in thickness of the transparent film becomes opticalnoise. Hence, there exists a problem in which the target defect is to berevealed while reducing influences from the non-uniformity in theintensity of interference light. In addition, to stably produce LSI, itis required to control the state of failures in LSI devices; for thispurpose, it is desirable to inspect all LSI substrates. Consequently,there exists a problem which the target defect is to be detected in ashort period of time.

It is therefore another object of the present invention to provide adefect detection device and a defect detection method to detect variousdefects on a wafer at a high speed and with high sensitivity and adefect observation device on which they are mounted.

Solution to Problem

Description will be given hereinafter of aspects for outlines ofrepresentative ones of the inventions disclosed by the presentapplication to achieve either one of the objects above.

(1) A defect detection device, characterized by comprising aillumination optical system for emitting laser onto a surface of aninspection target object in an inclined direction; and a detectionoptical system for focusing, by an objective lens, scattered light fromthe inspection target object due to the laser emitted as above, tothereby form an image on a solid-state imaging element, wherein thedetection optical system comprises a distribution filter for controllinga polarization direction of scattered light, included in the scatteredlight, due to roughness of the inspection target surface and apolarization direction of scattered light, included in the scatteredlight, due to foreign matter or a defect on the inspection target objectsurface, to thereby select a polarization direction of light to betransmitted.(2) A defect observation device, characterized by comprising a defectdetection device comprising a illumination optical system for emittinglaser onto a surface of an inspection target object in an inclineddirection and a detection optical system for focusing, by an objectivelens, scattered light from the inspection target object due to the laseremitted as above, to thereby form an image on a solid-state imagingelement; and an electron microscope for conducting positioning based onpositional information, obtained by the defect detection device, of adefect or foreign matter on the inspection target object surface, tothereby observe the defect or the foreign matter, the detection opticalsystem of the defect detection device comprising a distribution filterfor controlling a polarization direction of scattered light, included inthe scattered light, due to roughness of the inspection target surfaceand a polarization direction of scattered light, included in thescattered light, due to foreign matter or a defect on the inspectiontarget object surface, to thereby select a polarization direction oflight to be transmitted.(3) A dark-field defect inspection method in which a signal of scatteredlight appearing, due to illumination light emitted onto a surface of aninspection target object, from the inspection target object surface isobtained by a first sensor of a detection system and foreign matter or adefect on the inspection target object is detected based on the signalobtained by the first sensor, characterized by comprising anillumination light monitoring step of measuring either one or both of anintensity distribution and a polarization state distribution of theillumination light, a detection system monitoring step of detecting, bydetecting light inputted to the detection system by a second sensor, afocusing characteristic of a detection lens and an operation state of astage on which the inspection target object is to be placed; and afeedback control step of comparing a detection result of theillumination light monitoring step and a detection result of thedetection system monitoring step with an ideal value and adjustingeither one or both of the illumination light and the detection system tomake a difference between each of the detection results and the idealvalue equal to or less than an allowable value.

Advantageous Effects of Invention

According to the present invention, when precisely observing, by an SEMor the like, the defect detected by an optical defect inspection device,it is possible to surely place the defect as the observation target inthe observation visual field of the SEM; hence, it is possible toincrease the throughput of the precise inspection of the defect usingthe SEM and the like. Also, the device can be configured at a low costand in a small size.

Or, it is possible to detect various defects on a substrate at a highspeed and with high sensitivity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an example of a configuration of a defectobservation device in a first embodiment of the present invention.

FIG. 2 is a diagram showing in detail a dark-field lighting unit in thefirst embodiment of the present invention.

FIG. 3 is a diagram showing in detail an optical height detection devicein the first embodiment of the present invention.

FIG. 4 is a diagram showing in detail an optical microscope in the firstembodiment of the present invention.

FIG. 5 is a diagram showing in detail a scheme to change over adistribution polarization element in the first embodiment of the presentinvention.

FIG. 6 is a diagram showing in detail another example of the scheme tochange over a distribution polarization element in the first embodimentof the present invention.

FIG. 7 is a diagram showing an example of the distribution direction ofthe transmission axis of a distribution polarization element to beinserted in an optical microscope pupil plane 112 in the firstembodiment of the present invention.

FIG. 8 is a diagram showing an example of the contour of the spatialfilter to be inserted in the optical microscope pupil plane 112 in thefirst embodiment of the present invention.

FIG. 9 is a diagram to explain scattered light simulation conducted todetermine an optical characteristic of the distribution polarizationelement and the spatial filter in the first embodiment of the presentinvention.

FIG. 10 is a diagram showing an example of results of the scatteredlight simulation conducted to determine an optical characteristic of thedistribution polarization element and the spatial filter in the firstembodiment of the present invention.

FIG. 11 is a diagram showing an example of the distribution direction ofthe transmission axis of a distribution polarization element to beinserted in the optical microscope pupil plane 112 in the firstembodiment of the present invention.

FIG. 12 is a diagram showing an example in which the distributionpolarization element and the spatial filter to be inserted in theoptical microscope pupil plane 112 are formed on one substrate in thefirst embodiment of the present invention.

FIG. 13 is a diagram showing a positional shift quantity calculationimage of a defect obtained through dark-field observation by the opticalmicroscope in the first embodiment of the present invention.

FIG. 14 is a diagram showing a procedure of defect observation in thefirst embodiment of the present invention.

FIG. 15 is a diagram showing a procedure of Z position calculation inthird and fourth embodiments of the present invention.

FIG. 16 is a diagram showing in detail a second configuration example ofthe optical microscope in the first embodiment of the present invention.

FIG. 17 is a diagram showing in detail a third configuration example ofthe optical microscope in the first embodiment of the present invention.

FIG. 18 is a diagram showing an example of a configuration of a defectobservation device in a second embodiment of the present invention.

FIG. 19 is a diagram showing an example of a configuration of a defectobservation device in a third embodiment of the present invention.

FIG. 20 is a diagram showing an example of a configuration of a defectobservation device in a fourth embodiment of the present invention.

FIG. 21 is a diagram showing an example of intensity distribution foreach polarization of the scattered light intensity from the substratesurface and intensity distribution for each polarization of thescattered light intensity from foreign matter obtained by use ofscattered light simulation.

FIG. 22 is a diagram showing an example in which a phase shifter isemployed in the vicinity of the optical microscope pupil plane 112 inthe first embodiment of the present invention.

FIG. 23 is a diagram to explain a change in the radial polarization whena phase shifter is employed in the vicinity of the pupil plane 112.

FIG. 24 is a diagram showing an example of division of the pupil plane112 and an example of a distribution polarization element in which thepupil plane 112 is divided into eight regions and the ratio between theforeign matter scattered light and the substrate surface scattered lightis obtained for each region by scattered light simulation to select apolarization direction for which the ratio between the foreign matterscattered light and the substrate surface scattered light is large.

FIG. 25 is a diagram showing an example in which a wave plate isemployed in the vicinity of the optical microscope pupil plane 112 inthe first embodiment of the present invention.

FIG. 26 is a diagram to explain a change in the polarization when a waveplate is employed in the vicinity of the pupil plane 112.

FIG. 27 is a diagram showing an example in which a polarizationdirection controller using liquid crystal is employed in the vicinity ofthe optical microscope pupil plane 112 in the first embodiment of thepresent invention.

FIG. 28 is a diagram to explain a change in the polarization directionby the polarization direction controller.

FIG. 29 is a diagram showing an example to explain a polarizationdirection controller using liquid crystal.

FIG. 30 is a diagram showing an example of a polarization directioncontroller which has optical rotatory power when not applied with avoltage and which loses the rotatory power when applied with a voltage.

FIG. 31 is a diagram showing an example of a polarization directioncontroller using liquid crystal in which the polarization direction canbe controlled based on the rubbing of the alignment film.

FIG. 32 is a diagram showing an example in which a polarizationdirection controller using a transparent magnetic substance is arrangedin the vicinity of the optical microscope pupil plane 112 in the firstembodiment of the present invention.

FIG. 33 is a diagram showing an example of a polarization directioncontroller using a transparent magnetic substance.

FIG. 34 is a diagram showing an example of a distribution filterincluding a combination of a polarization element and a mask in whichthe ratio between the foreign matter scattered light and the substratesurface scattered light is derived from scattered light simulation so asto transmit light in a region with the ratio more than a threshold valueand to block light in a region with the ratio between the foreign matterscattered light and the substrate scattered light less than a thresholdvalue.

FIG. 35 is a diagram showing an example of foreign matter scatteredlight and a substrate distribution polarization element in which thepupil plane 112 is divided into regions and the ratio between theforeign matter distributed light and the substrate surface distributedlight is derived for each region through scattered light simulation suchthat there is selected a polarization direction in which the ratiobetween the foreign matter scattered light and the substrate scatteredlight is large, and light is transmitted in a region with the ratio morethan a threshold value.

FIG. 36 is a diagram showing a configuration example of a defectdetection device of a defect observation device in the fifth embodimentof the present invention.

FIG. 37 is a diagram showing an example of the spatial filter to bedisposed in the vicinity of the pupil plane 112 to exclude scatteredlight caused by the pattern.

FIG. 38 is a block diagram showing an inner configuration of acontroller according to the fifth embodiment of the present invention.

FIG. 39 is a flowchart showing a monitoring processing procedure in thedefect observation device according to the fifth embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

Next, description will be given in detail of embodiments of the presentinvention by referring to the drawings according to necessity.

FIG. 1 shows an example of a configuration of a defect observationdevice in an embodiment of the present invention. The defect observationdevice of this embodiment is a device to observe, in the deviceproduction process to form circuit patterns on a substrate (wafer) of asemiconductor device or the like, defects taking place during theproduction process, and includes a wafer 1 as an inspection target, asample holder 2 to mount the sample thereon, a stage 3 capable of movingthe sample holder 2 to move the overall surface of the sample 1 beneatha microscope, an electron microscope (to be referred to as an SEMhereinafter) 5 to precisely observe the inspection target wafer 1, anoptical height detection system (to be referred to as a Z sensorhereinafter) 4 to align the focal point of the electron microscope 5with the surface of the sample 1, an optical microscope 14 whichoptically re-detects a defect of the sample 1 to obtain detailedpositional information of the defect on the sample 1, a Z sensor 7 tofocus the optical microscope 14, a vacuum chamber 6 to accommodate theelectron microscope 5 and an objective lens 105 of the opticalmicroscope 14, a controller 10 to control the electron microscope 5, theZ sensor 4, the Z sensor 7, a height control unit 106, and a solid-stateimaging element 111; a user interface 11, a database 12, and a network13 to connect to an upper system such as an optical defect detectiondevice.

In addition, the optical microscope 14 includes a dark-field lightingunit 101, a light introduction mirror 102 which introduces laser emittedfrom the dark-field lighting unit 101 to the vacuum chamber and controlsthe lighting position on the surface of the sample 1, a vacuum sealwindow 103, a mirror 104, an objective lens 105 to gather scatteredlight from the sample 1 or to conduct bright-field observation, anobjective height control unit 106, a vacuum seal window 107, ahalf-silvered mirror 108 to introduce light required for thebright-field observation, a bright-field light source 109, an imagingoptical system 110 to form an image of the sample 1 onto a solid-stateimaging element, a solid-state imaging element 111, and a distributionpolarization element and spatial filter change-over unit 401 (referenceis to be made to FIG. 5). Moreover, the stage 3, the Z sensors 4 and 7,the SEM 5, the user interface 11, the database 12, the height controlunit 106, and the solid-state imaging element 111 are connected to acontrol system 10, and the control system 10 is coupled via the network13 with an upper system (not shown).

In the defect observation device configured as above, particularly, theoptical microscope 14 includes a function to re-detect (to be expressedas detect hereinafter) the position of a defect on the sample detectedby an optical defect inspection device (not shown), by use of positionalinformation of the defect detected by the optical defect inspectiondevice; the height control unit 106 and the Z sensor 7 have a functionas a focusing unit to conduct the sample focusing operation; the controlsystem 10 has a function as a position correction unit to correct thedefect positional information based on defect positional information ofa defect detected by the microscope 14; and the SEM 5 has a function toobserve the defect for which the positional information is corrected bythe control system 10. The stage 3 on which an inspection target wafer 1is mounted moves between the optical microscope 14 and the SEM 5 so thatthe defect detected by the optical microscope 14 is observed by the SEM5.

The objective 105 and the height control unit 106 are installed in thevacuum chamber 6. As for the configuration of the height control unit106, it may be configured to be moved by using, for example, apiezoelectric element; to be moved in the Z direction (the directionalong the optical axis 115 of the imaging optical system 110) by use ofa stepping motor and a ball screw; or to be moved in the Z directionalong the linear guide by use of an ultrasonic motor and a ball screw.

The light introduction mirror 102 is employed to introduce light emittedfrom the illumination light source 101 into the vacuum chamber 6 asshown in FIG. 1. Incidentally, the light introduction mirror 102 mayinclude, in order to control a lighting position on the surface of thesample 1, a mechanism which rotates about two axes including an axisalong the longitudinal direction of the mirror shown and an axisperpendicular to the drawing.

Next, description will be given in detail of the respective componentsby referring to FIGS. 2 to 20.

FIG. 2 shows the dark-field lighting unit 101 in detail. The dark-fieldlighting unit 101 includes a illumination light source 501 to emit, forexample, visible light laser, ultraviolet light laser, or vacuumultraviolet light laser; an optical filter 502 to adjust intensity ofillumination light, a wave plate 503 to adjust the polarizationdirection of illumination light, and a lens group 507 to focus theillumination light onto the sample 1. The lens group 507 includes aplano-concave lens 504, an achromat lens 505, and a cylindrical lens506. In this mechanism, by selecting the lens focal distance and byadjusting the gap between lenses, the lighting area on the surface ofthe sample 1 may be controlled in a range from the overall visual fieldto the diffraction limit of the optical microscope 14; although there isemployed skewed lighting due to the cylindrical lens, a circularradiation area is feasible.

The illumination light source 501 is a laser oscillator. The laseroscillator oscillates to emit, for example, visible light of 405 nm, 488nm, and 532 nm (400 nm to 800 nm) or ultraviolet light of 400 nm orless, or vacuum ultraviolet light of 200 nm or less; and both of acontinuous wave oscillation laser and a pulse oscillation laser may beemployed. As for the selection method thereof, when a continuous waveoscillation laser is employed, it is not expensive and stable, and it ispossible to implement a small-sized device. The wavelength of theillumination light source 501 is not restricted by the wavelengthsdescribed above. If high sensitivity is required, ultraviolet light isemployed; in this situation, the objective 105, the vacuum seal window107, the half-silvered mirror 108, and the imaging optical system 110include optical elements or reflection-type optical elements for theultraviolet zone of synthetic quartz or the like. If higher sensitivityis required, vacuum ultraviolet light is employed; in this situation,the objective 105, the vacuum seal window 107, the half-silvered mirror108, and the imaging optical system 110 include optical elements orreflection-type optical elements for the vacuum ultraviolet zone ofdissolved quartz or the like; further, in order to prevent absorption ofthe propagating vacuum ultraviolet light, the overall optical path ofthe microscope 14 is installed in vacuum or in, for example, nitrogengas atmosphere. Since the object is to propagate the vacuum ultravioletlight, the gas to be filled in is not limited to nitrogen.

To emit light onto the sample 1, p-polarized laser light is employed ifthe sample 1 is a mirror wafer; and s-polarized laser light is used ifthe surface of the sample 1 is coated with a metallic thin film.Linearly polarized light of p-polarized or s-polarized light is employedto more efficiently observe scattered light to implement the observationwith an appropriate S/N. That is, in the observation of a mirror wafer,if the s-polarized light is employed, the scattering power isdeteriorated to reduce the absolute amount of scattered light and theefficiency is lowered; hence, the illumination of p-polarized light issuitable; on the other hand, if illumination of p-polarized light isused to observe a metallic thin film or the like, scattered light fromthe substrate is strong, and fine defects and fine foreign matter cannotbe observed; hence, illumination of s-polarized light is suitable

Further, to suppress the scattered light from the substrate, thelighting is conducted with a low elevation angle of about 10° withrespect to the substrate surface. The mirror 104 includes a mechanism(not shown) to move, even when the objective 105 goes upward ordownward, together with the objective to thereby light the visual fieldof the objective 105. Or, the mirror 104 may include an independentlymovable mechanism (not shown) to change the lighting position in thevisual field of the objective 105.

FIG. 3 shows the Z sensor 4 or 7. The Z sensor 4 or 7 includes a lightsource 751 to emit height measuring light, a slit 703, a focusing lens702 to focus the height measuring light emitted from the lighting unit751 onto the slit 703, an imaging lens 704 to form an image (an image ofthe slit 703) of light having passed the slit 703 as the heightmeasuring light, on the surface of the sample 1; a focusing lens 705 tofocus the height measuring light reflected by the sample 1, and adetector 706 to detect the height measuring light focused by thefocusing lens 705 to convert it into an electric signal. Information ofthe height measuring light converted by the detector 706 into anelectric signal is sent to the control system 10 for the calculation ofthe height. Incidentally, as the detector 706, there is employed atwo-dimensional CCD or line sensor or a 2-division or 4-divisionposition sensor.

FIG. 4 shows in detail the configuration of the optical microscope 14.The optical microscope 14 includes a dark-field lighting unit 101, alight introduction mirror 102, a mirror 104, an objective 105, a heightcontrol unit 106, a half-silvered mirror 108, a bright-field lightsource 109, an imaging optical system 110, and a solid-state imagingelement 111. The imaging optical system 110 includes a lens 113 a toobtain a pupil plane 112 a of the objective 105, a lens 113 b to focusan image, and a filter unit 114 to be inserted in the obtained pupilplane 112 b. An example of the filter unit 114 is a distributionpolarization element. According to the present embodiment, theconfiguration of the filter unit 114 makes it possible that a pluralityof distribution polarization elements having different characteristicsare held by a holder 401 (four kinds thereof 114 a to 114 d in theexample shown in FIG. 5) in the filter unit 114 and a changeoveroperation is conducted between the distribution polarization elements114 a to 114 d for the insertion thereof in the pupil plane 112 b.Further, the height control unit 106 and the solid-state imaging element111 are connected to the control system 10.

The lens 113 a is used to draw the pupil plane 112 of the objective 105to the outside to form it in the imaging optical system 110; by drivingthe holder 402, a distribution polarization element selected from thedistribution polarization elements 114 a to 114 d held by the holder 402is inserted in the pupil plane 112 drawn into the imaging optical system110. The holder 402 may insert, in place of the distributionpolarization elements 114 a to 114 d, a spatial filter or a distributionpolarization element formed on the spatial filter. The lenses 113 a and113 b are paired to focus an image of the sample 1 onto the detectionsurface of the solid-state imaging element 111.

The ratio between reflection and transmission may be arbitrarily set inthe half-silvered mirror 108. However, when the light intensity from thebright-field light source 109 is sufficiently secured, it is favorableto configure such that much scattered light from the defect is fed tothe imaging optical system 110 and the solid-state imaging element 111.

For the bright-field light source 109, a lamp or a laser may be used.When a laser is used, it is possible, by substituting a dichroic mirrorfor the half-silvered mirror 108, to make the lighting brighter and tofeed much scattered light to the solid-state imaging element 111. Or, inthe dark-field observation, there may be disposed a mechanism (notshown) to remove the half-silvered mirror 108 from the optical axis 115of the imaging optical system 110 and the objective 105. In suchsituation, much scattered light can be advantageously fed to thesolid-state imaging element 111.

FIG. 5 shows a changeover unit 401 to conduct a changeover operation, onthe optical axis 115 of the imaging optical system 110, for thedistribution polarization elements 114 a to 114 d inserted in the pupilplane 112 b of the objective 105. The unit 401 includes in itsconfiguration a holder 402 to arrange a plurality of distributionpolarization elements 114 a to 114 d having different characteristicsand a rotation drive unit 403 for an axis to rotate the holder 402. Theholder 402 is a unit to conduct a changeover operation to select eitherone of the distribution polarization elements 114 a to 114 d accordingto the kind of the fine defect to be detected. On the other hand, in thebright-field observation, to avoid disturbance in the obtained image,the holder 402 is placed for the observation at a position other thanthe places where the distribution polarization elements 114 a to 114 dare arranged. Or, the position is changed to a place where a sheet ofparallel planar glass with thickness equal to that of the distributionpolarization elements 114 a to 114 d is installed. The sheet of parallelplanar glass with thickness equal to that of the distributionpolarization elements 114 a to 114 d is installed to avoid an event inwhich when the distribution polarization elements 114 a to 114 d areremoved, the optical path length changes and the image of the sample 1is not focused onto the solid-state imaging element 111. Or, withoutinstalling the sheet of parallel planar glass, there may be employed amechanism in which the image is focused onto the solid-state imagingelement 111 by adjusting the position of the image focusing lens 113 bor the solid-state imaging element 111.

In conjunction with the embodiment shown in FIG. 5, description has beengiven of a situation in which a plurality of distribution polarizationelements 114 a to 114 d having different characteristics are installedin the holder 402; however, it is also possible that in place of theplural distribution polarization elements 114 a to 114 d, a plurality ofspatial filters having different characteristics are installed in theholder 402 to conduct the changeover operation. In a situation in whichthe spatial filters are installed in the holder 402 and the bright-fieldobservation is conducted, to avoid disturbance in the obtained image,the position of the holder 402 is set to other than the place where thespatial filters are installed for the observation. Or, the changeover iscarried out to a place in the holder 402 where a sheet of parallelplanar glass having thickness equal to that of the spatial filters isinstalled. Or, or, without installing the sheet of parallel planarglass, there may be used a mechanism in which the image is focused ontothe solid-state imaging element 111 by adjusting the position of theimage focusing lens 113 b or the solid-state imaging element 111.

FIG. 6 shows another embodiment of the mechanism to move thedistribution polarization elements 114 a to 114 d. The mechanism 410 isa mechanism in which the distribution polarization element holder 405slides to move a distribution polarization element 114 e onto and fromthe optical axis 115 of the imaging optical system 110. Although FIG. 6shows a situation in which one distribution polarization element 114 eis used, there may be included a plurality of distribution polarizationelements. Further, also in this embodiment, a spatial filter may be usedin place of the distribution polarization element 114 e. In addition, itis possible to combine the distribution polarization element 114 withthe spatial filter.

In FIG. 7, (a) and (b) show polarization characteristic examples of thedistribution polarization elements 114 a and 114 b to be inserted in thepupil plane 112 b in the imaging optical system 110. 1002 indicates apupil outer circumference and 9001 indicates a transmission polarizationaxis direction. The distribution polarization elements 114 a and 114 bhave a diameter of the size at least covering the overall pupil plane1121002, and the transmission polarization axis direction 9001 varies atrespective points of the distribution polarization elements 114 a and114 b.

In the plane, the distribution polarization elements 114 a and 114 b inwhich the transmission polarization axis direction 9001 is distributedare implemented by linking linear polarization elements together, byusing photonic crystal, by using wire grid polarizer, or by combiningliquid crystal with a polarization element. Here, the photonic crystalis an optical element including fine structures in which the refractiveindex varies with a period of a light wavelength or less, and the wiregrid polarizer is a polarization element in which electricallyconductive fine wires are periodically arranged to provide opticalanisotropy.

In FIG. 8, (a) to (d) show an example in which in place of thedistribution polarization elements 114 a to 114 d exemplified as filters114 in FIG. 5, spatial filters 1000 a to 1000 d are inserted in thepupil plane 112. In this example, in the changeover mechanism 401 shownin FIG. 5, the spatial filters 1000 a to 1000 d having differentcontours are installed in place of the plural distribution polarizationelements 114 a to 114 d. In (a) to (d) of FIG. 8, 1002 indicates a pupilouter circumference and 1003 to 1006 indicate light block zones.

The value of I of the light block zone 1003 in the spatial filter 1000 ashown in FIG. 8( a) and the values of θ and φ of the light block zone1004 in the spatial filter 1000 b shown in FIG. 8( b) are determinedbased on the scattered light intensity distribution obtained throughscattered light simulation or actual measurement of scattered light.

Description will be given of an example of the method of determining thetransmission polarization axis direction 9001 and the value of I or thevalues θ and φ of the spatial filter contour by referring to FIGS. 9 and10.

First, description will be given of the scattered light simulation andterms required to determine the transmission polarization axis direction9001 of the distribution polarization elements 114 a to 114 d byreferring to FIG. 9. In the scattered light simulation, laser as theillumination light is emitted onto the sample 1 from above in a skeweddirection and then light scattered by fine foreign matter or finedefects placed on the sample 1 is used to calculate the intensitydistribution and the polarization distribution of scattered light on asurface nearest to the sample 1 of the optical element nearest to thesample 1 of the imaging optical system. As for the polarized light ofscattered light, it is assumed that the polarized light parallel to theincidence plane is p-polarized light and the polarized light withpolarization perpendicular to that of the p-polarized light iss-polarized light. Additionally, in the plane in which the intensitydistribution or the polarization distribution is obtained, the halfthereof on the side of the illumination incidence 700 is referred to asan incidence side and the remaining half thereof is referred to as anemission side hereinafter.

Next, description will be given of a method of determining the polarizedlight transmission axis distribution h(r,θ) of the distributionpolarization elements 114 a to 114 d and the light block zone g(r,θ) ofthe spatial filters 1000 a to 1000 d.

First, through scattered light simulation, there are obtained thescattered light intensity distribution fs(r,θ) of scattered light fromfine defects or fine foreign matter to be detected with highsensitivity, the p-polarized light distribution psp(r,θ) and thes-polarized light distribution pss(r,θ) of the scattered light as wellas the scattered light intensity distribution fN(r,θ) of scattered lightfrom fine concavity and convexity on the substrate surface, and thep-polarized light distribution pNp(r,θ) and the s-polarized lightdistribution pNS(r,θ) of the scattered light.

The polarized light transmission axis direction distribution h(r,θ) ofthe distribution polarization element 114 is determined as apolarization axis distribution which most blocks scattered light fromfine concavity and convexity on the substrate surface, that is, h(r,θ)which minimizes π of (MATH.1); or, a polarization axis distributionwhich most transmits scattered light from a fine defect or fine foreignmatter, that is, h(r,θ) which maximizes Λ of (MATH.2); or, apolarization axis distribution which blocks the scattered light fromfine concavity and convexity on the substrate surface and whichtransmits scattered light from a fine defect or fine foreign matter,that is, h(r,θ) which maximizes Ω of (MATH.3).

$\begin{matrix}{\Pi = {\int{\sqrt{{{{p_{NP}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2} + {{{p_{NS}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2}}{r}{\theta}}}} & \left\lbrack {{MATH}.\mspace{14mu} 1} \right\rbrack \\{\Lambda = {\int{\sqrt{{{{p_{SP}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2} + {{{p_{SS}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2}}{r}{\theta}}}} & \left\lbrack {{MATH}.\mspace{14mu} 2} \right\rbrack \\{\Omega = \frac{\int{\sqrt{{{{p_{SP}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2} + {{{p_{SS}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2}}{r}{\theta}}}{\int{\sqrt{{{{p_{NP}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2} + {{{p_{NS}\left( {r,\theta} \right)} \cdot {h\left( {r,\theta} \right)}}}^{2}}{r}{\theta}}}} & \left\lbrack {{MATH}.\mspace{14mu} 3} \right\rbrack\end{matrix}$

On the other hand, the method to determine the light block zone g(r,θ)of the spatial filter is, for example, a method in which the light blockzone g(r,θ) is optimized to maximize represented by (MATH.4).

$\begin{matrix}{\Psi = \frac{\int{{f_{S}\left( {r,\theta} \right)} \times {g\left( {r,\theta} \right)}{r}{\theta}}}{\int{{f_{N}\left( {r,\theta} \right)} \times {g\left( {r,\theta} \right)}{r}{\theta}}}} & \left\lbrack {{MATH}.\mspace{14mu} 4} \right\rbrack\end{matrix}$

More simply, there may also be used a method wherein the spatial filterhas a distribution to block light in the zone in which the scatteredlight from the fine concavity and convexity on the substrate surface isstrong or a method wherein the spatial filter having a distribution toblock light in the zone in which the scattered light from the fineconcavity and convexity on the substrate surface is strong is combinedwith the linear polarization element.

Next description will be given of the method of determining thepolarized light transmission axis direction distribution of thedistribution polarization elements 114 a to 114 d and the light blockcharacteristic of the spatial filters 1000 a to 1000 d by specificallyusing an example of scattered light simulation results.

In FIGS. 10, (a) to (f) show examples of the scattered lightpolarization distribution, calculated by scattered light simulation, ofscattered light from polystyrene latex (to be referred to as PSLhereinafter) as fine depressions, projections, and a fine particle on asurface of the inspection target wafer 1.

FIG. 10( a) shows the distribution of p-polarized light of the scatteredlight (light wavelength 400 nm) by 30 nm PSL, FIG. 10( b) shows thedistribution of s-polarized light of the scattered light by 30 nm PSL,FIG. 10( c) shows the distribution of p-polarized light of the scatteredlight by the concavity and convexity on a surface of the inspectiontarget wafer 1, FIG. 10( d) shows the distribution of s-polarized lightof the scattered light by the fine concavity and convexity on a surfaceof the inspection target wafer 1, FIG. 10( e) shows the p-polarizedlight distribution of the ratio (to be indicated as S/N hereinafter)between the scattered light from PSL and that from the concavity andconvexity on a surface of the inspection target wafer 1, and FIG. 10( f)shows the s-polarized light distribution of S/N.

From FIG. 10( a) and FIG. 10( b), it can be seen that in the scatteredlight by PSL, the p-polarized light is strong in the outercircumferential units of the pupil plane 112 on the illuminationincidence 700 side and the illumination emission 701 side; and thes-polarized light is strong in the outer circumferential units of thepupil plane 112 in the direction vertical thereto. On the other hand,from FIG. 10( c) and FIG. 10( d), it can be seen that in the scatteredlight from the concavity and convexity on a surface of the inspectiontarget wafer 1, the p-polarized light is strong on the illuminationincidence 700 side; and in the direction of the illumination incidenceside 700 direction ±45°, the p-polarized light is equal in strength tothe s-polarized light, that is, it is 45°-polarized light. Further, fromFIG. 10( c) and FIG. 10( d), it can be seen that on the illuminationemission 701 side, the scattered light taking place from the concavityand convexity on a surface of the inspection target wafer 1 is veryweak.

FIGS. 10( e) and 10(f) show S/N calculated based on FIGS. 10( a) to10(d). FIG. 10( e) shows S/N of p-polarized light and FIG. 10( f) showS/N of s-polarized light.

The distribution polarization element 114 configured to have thedistribution of the polarized light transmission axis direction 9001 toblock the scattered light from the concavity and convexity on a surfaceof the inspection target wafer 1 can be determined as exemplified inFIG. 7( a) and FIG. 7( b), according to, for example, FIG. 10( c) andFIG. 10( d). FIG. 7( a) and FIG. 7( b) exemplify the distributioncontours of the polarized light transmission axis direction 9001 of thedistribution polarization element 114 in which 1002 indicates the edgeof the distribution polarization element and 9001 indicates thepolarized light transmission axis direction. Over the line ofintersection between the incidence plane of the illumination light andthe pupil plane 112 and in the neighborhood thereof, the s-polarizedlight is transmitted; in the direction skewed ±45° with respect to thedirection of the illumination incidence 700, the ±45°-polarized light istransmitted; on the side of the illumination emission 701 of the pupilplane 112, the p-polarized light is transmitted; and in the pupilcentral unit and the pupil periphery in the direction vertical to theillumination incidence, the s-polarized light transmission distributionis obtained. Further, the distribution contour of the polarized lighttransmission axis direction 9001 to gather the scattered light from PSLto the maximum extent is determined based on the scattered lightdistribution characteristic shown in FIG. 10( a) and FIG. 10( b); thecontour is formed, for example, as the polarized light transmission axisdirection 9001 in a concentric shape parallel to the outer circumferenceof the pupil plane 112 as shown in FIG. 11.

Also, the distribution contour of the polarized light transmission axisdirection 9001 to transmit the polarized light in which the ratio of thescattered light from the fine defect or fine foreign matter to thescattered light from the fine concavity and convexity on a surface ofthe inspection target wafer 1 is high can be determined using FIG. 10(e) and FIG. 10( f); the contour is formed, for example, as the polarizedlight transmission axis direction 9001 to transmit only the p-polarizedlight in the pupil outer circumference unit on the side of theillumination emission 701.

Incidentally, the intensity distribution and the polarizationdistribution of the scattered light vary depending on the contour andthe size as well as optical characteristics such as the refractive indexof the fine foreign matter or a fine defect to be detected; hence, thepolarization distribution of the distribution polarization element to beinserted in the pupil plane 112 of the imaging optical system is notlimited to the distribution contours of the polarized light transmissionaxis direction 9001 shown in FIG. 7( a) and FIG. 7( b).

In FIG. 8, (a) to (d) show examples of the contour of the spatialfilters 1000 a to 1000 d. It is only required that the diameter d of thespatial filters 1000 a to 1000 d is equal to or more than the pupildiameter, and the centers of the spatial filters 1000 a to 1000 d arearranged to match the optical axis 115 of the imaging optical system110, and there are included light block zones 1003 to 1006. FIG. 8( a)is the spatial filter 1000 a in which the edge of the light block zone1003 is appropriately vertical to the incidence direction 700 of thedark-field lighting; in the example of FIG. 8( a), I<d/2 and the lightis blocked in a part of the incidence side of the pupil in thisconfiguration. The spatial filter 1000 a shown in FIG. 8( a) may be usedto block p-polarized light of scattered light taking place due to fineconcavity and convexity on a surface of the inspection target wafer 1shown in FIG. 10( c), and it functions, by setting substantially I=d/2,as a spatial filter to block both of the p-polarized light and thes-polarized light of the scattered light taking place due to the fineconcavity and convexity on a surface of the inspection target wafer 1.However, depending on the contour and the size of the fine defects orthe fine foreign matter as the observation target or the sensitivityrequired for the measurement, it is also possible to use a spatialfilter set as I>d/2. For example, when it is desired to selectivelydetect an area having a high N/S as shown in FIG. 10( e), I issubstantially 0.8 d.

FIG. 8( b) shows an example of the spatial filter 1000 b including alight block zone 1004 to block light in an area having the shape of asector with an azimuth of φ and a vertex angle of θ in the pupil. In thespatial filter 1000 b of FIG. 8( b), the vertex of the sector of thelight block zone 1004 is aligned with the center (the optical axis 115of the imaging optical system 110) of the pupil plane 112; however, itis not necessarily required that the vertex of the light block zone 1004matches the optical axis 115 of the imaging optical system 110. Thespatial filter 1000 b shown in FIG. 8( b) is an example of the spatialfilter to block only the p-polarized light of the scattered light due tothe fine concavity and convexity on a surface of the inspection targetwafer shown in FIG. 10( c). Incidentally, depending on the contour andthe size of the fine defects or the fine foreign matter as theobservation target or the sensitivity required for the measurement, theangle θ is determined and is freely selectable in the range of0°<θ<360°.

Additionally, as shown in FIG. 8( c), there may be used a spatial filter1000 c including a light block zone 1005 in the form of an island in thepupil. Or, there may be used a spatial filter 1000 d including a lightblock zone 1006 in the form of a combination of the spatial filters 1000a to 1000 c shown in (a) to (c) of FIG. 8.

The light block zones 1003 to 1006 of the spatial filters 1000 a to 1000d to be inserted in the pupil plane 112 b are configured by using, forexample, a light block plate of a metallic plate or the like processedto have a black frosted surface or a combination of a polarizationelement and liquid crystal or a digital mirror array.

Either one of the distribution polarization elements 114 a to 114 d andeither one of the spatial filters 1000 a to 1000 d to be inserted in thepupil plane 112 b may be formed on one substrate; FIG. 12( a) shows suchan example as a composite filter 1200. In the composite filter 1200shown in FIG. 12( a), 115 indicates an optical axis of an imagingoptical system 110, 1001 is a light block zone, and 9001 is atransmission polarization axis direction. The composite filter 1200which is exemplified in FIG. 12( a) and in which spatial filters anddistribution polarization elements are formed on one substrate is acombination of distribution polarization elements having a polarizationdistribution to block p-polarized light of the scattered light from thefine concavity and convexity on a surface of the inspection target wafer1 and to selectively obtain the scattered light from PSL. This is acombination of the polarized light transmission axis distribution h(r,θ)of the distribution polarization elements and the light block zoneg(r,θ) of the spatial filters to maximize both of Ω of (MATH.3) and Ψ of(MATH.4). As for a method of forming, on one substrate, either one ofthe distribution polarization elements 114 a to 114 d and either one ofthe spatial filters 1000 a to 1000 d, there may be considered photoniccrystal, a combination of a polarization element and liquid crystal, acombination of a light block plate and a wire grid polarizer, and thelike.

Either one of the distribution polarization elements 114 a to 114 d andeither one of the spatial filters 1000 a to 1000 d to be inserted in thepupil plane 112 b may be combined with each other at the same time; FIG.12( b) shows an example as a composite filter 1201. In the compositefilter 1201 shown in FIG. 12( b), 115 indicates an optical axis of theimaging optical system 110, 1001 is a light block zone, and 9001 is atransmission polarization axis direction.

Incidentally, the intensity distribution of the scattered light variesdepending on the contour and the size as well as optical characteristicssuch as the refractive index of the fine foreign matter or fine defectsto be detected; hence, the light block characteristic of the spatialfilter to be inserted in the pupil plane 112 b of the imaging opticalsystem is not limited to the contours shown in (a) and (b) of FIG. 8. Itis only necessary that the spatial filter has a contour to block thescattered light component in association with the distributioncharacteristic of the scattered light due to the fine concavity andconvexity on a surface of the inspection target wafer 1.

Description will be given of operation in the configuration of thedefect observation device shown in FIG. 1. First, the sample 1 istransported via a load lock chamber, not shown, onto the sample holder 2in the vacuum chamber 6. And the sample 1 is moved, under control of thestage 3, into the visual field of the optical microscope 14. At thispoint, it is likely that the sample 1 is apart from the position of thefocus of the optical microscope. If the height of the sample 1 is apartfrom the position of the focus, the objective 105 and the mirror 104 aremoved in the Z direction by use of the height control unit 106 such thatthe sample 1 is set to the position of the focus of the opticalmicroscope 14. The method of determining the quantity of movement in theZ direction will be described later.

To observe defects on the wafer 1 mounted on the stage 3 of the defectobservation device shown in FIG. 1 by use of positional information ofdefects on the wafer 1 detected by another defect inspection device (notshown), it is required to conduct wafer alignment to match the referenceposition of the wafer 1 with the reference of the stage 3. The waferalignment is conducted by using bright-field observation images. Atbright-field detection, illumination light is emitted from thebright-field lighting unit 109, and the light is reflected by thehalf-silvered mirror 108 to be radiated through the objective 105 ontothe sample 1. Reflected light from the sample 1 passes the imagingoptical system 110 to form an image on the solid-state imaging element111. Here, the bright-field lighting unit 109 is, for example, a lamp.In the bright-field observation of the present embodiment, the filter114 to be inserted in the imaging optical system 110 is replaced by asheet of parallel planar glass having the same thickness. If thealignment is conducted using the outer contour of the sample 1 (forexample, an orientation flat or notch if the sample 1 is a wafer), it isonly required to carry out the process by obtaining images at thepositioning point and several points of the outer contour of the sample1.

After the wafer alignment, according to the positional information ofthe defects detected by the defect inspection device, the defect ismoved into the visual field of the optical microscope 14 to obtain adefect image in the dark-field observation method of the opticalmicroscope 14. In the operation, for each defect position, if the heightof the sample 1 is apart at each defect position from the position ofthe focus of the optical microscope 14, the focusing is carried out in amethod, which will be described later.

Next, the dark-field observation method will be described. In thedark-field observation method, illumination light is emitted from thelighting unit 101. Although the illumination light may be laser light orlamp light, the laser light is desirably employed since higherilluminance is obtained by the laser light.

The light emitted from the lighting unit 101 is reflected by the lightintroduction mirror 102 and its direction is changed to the Z directionand the light is fed through the vacuum seal window 103 into the vacuumchamber 6, and its direction is changed by the mirror 104, and the lightis emitted onto a surface of the sample 1 existing at the position ofthe focus of the optical microscope 14. The light scattered by thesample 1 is gathered by the objective 105 and is fed to the imagingoptical system 110 to form an image on the imaging position of thesolid-state imaging element 111, and the image is converted into anelectric signal by the solid-state imaging element 111 to be sent to thecontrol system 10.

The image obtained in the dark-field observation method of the opticalmicroscope 14 is stored as a gray-scale image or a color image in thecontrol system 10. In the control system, as shown in FIG. 13,positional shift quantities 304 a and 304 b of the defect 302 relativeto the center position of the visual range 302 of the SEM 5 arecalculated, and the shift quantities are registered as coordinatecorrection values. Thereafter, by using the coordinate correctionvalues, the sample 1 is moved by the stage 3 such that the defect 303 isin the visual field 302 of the SEM 5, to thereby observe the defect. Theimage of the observed defect is transmitted to the control system 10 toexecute processing such as display of the image on the user interface11, registration thereof to the database, and automatic defectclassification.

Description will be given of a flow of the defect observation byreferring to FIG. 14.

First, the sample 1 is aligned (6001). This is conducted in the methoddescribed for the bright-field observation by the optical microscope 14.Next, by use of positional information of defects beforehand detected byanother defect inspection device, the stage 3 is moved such that thedefect on the sample 1 to be observed is in the visual filed of theoptical microscope 14 (6002). Next, the objective 105 is moved by theheight control unit 106 to conduct the focusing (6003).

A search is made for a defect in the image obtained by the opticalmicroscope 14 and the solid-state imaging element 111 (6004); if adefect is detected (6005-yes), based on the difference between thedefect detection position by the optical microscope 14 and thepositional information of defects beforehand detected by another defectinspection device, the shift quantity of the visual field of the SEM 5for the defect in the observation of the defect by the SEM is calculatedby using the positional information of the defects beforehand detectedby another defect inspection device (6006). Based on the calculatedshift quantity, the positional information of defects beforehanddetected by another defect inspection device is corrected (6007), andthe defect for which the positional information is corrected is movedinto the visual field of the SEM 5 for the observation thereof (6008).In the operation, the observed information is sent to the control system10 and is registered to the database 11. Incidentally, if there exist alarge number of defects to be observed, several representative defectsare extracted therefrom; based on the positional information beforehanddetected for the extracted defects by another defect inspection deviceand the positional information of the respective defects obtainedthrough the detection by the optical microscope 14, there is obtainedthe shift quantity between the position of the defect beforehanddetected by another defect inspection device and the visual position ofthe SEM 6. By use of the obtained information of the shift quantity,also for defects which are other than the several representative defectsand which are not detected by the optical microscope 14, the positionalinformation of defects beforehand detected by another defect inspectiondevice is corrected.

Next, if defect information is not required (6009-no), the end ofobservation is assumed (60010); if defect information is required(6009-yes), defect positional information of a defect to be observed isobtained, and control returns to the procedure to move the defect to theoptical microscope 14 as described above, to execute processing.Incidentally, if no defect is detected in the defect detection proceduredescribed above (6005-no), it is likely that the defect is outside thevisual field of the optical microscope 14; hence, a search may be madethrough the periphery of the visual field of the optical microscope 14.If the search through the periphery is to be conducted (6012-yes), thesample 1 is moved by the distance corresponding to the visual field(6011) to execute the processing beginning at the defect detectionprocedure described above. Further, if the search through the peripheryis not to be conducted (6012-yes), the processing is executed accordingto the procedure.

There also exists a method in which for each defect, the correctionquantity of the defect position is beforehand calculated to beregistered to a database such that after the position correctionquantity calculation is finished for a plurality of defects or alldefects, the observation is conducted by the SEM 5.

Next, the method of calculating the Z position will be described byreferring to FIG. 3. FIG. 3 shows a configuration of the Z sensors 4 and6, and the configuration includes a light source 751, a focusing lens702, a slit 703, a projection lens 704, a light reception lens 705, anda detector 706. The illumination light source is, for example, a laseroscillator or a lamp, and the detector 706 is, for example, a CCD cameraor a CCD linear sensor.

Operation of the Z sensors 4 and 6 will be described. Light emitted fromthe illumination light source 751 is radiated through the light focusinglens 702 onto the slit 703 and is then focused through the projectionlens 704 onto a surface of the sample 1. Light reflected by the sample 1is gathered via the light reception lens 705 onto the detector 706. Inthe Z position calculation method, the light detection position of thedetector 706 when the sample 1 is at the reference height is firststored. Next, when the height changes, the position of the lightdetection in the detector 706 changes; hence, by beforehand measuringthe relationship between the quantity of movement of the light detectionposition and the change in the height of the sample 1, it is possible tocalculate the height of the sample 1 according to the change in thelight detection position.

In conjunction with the present embodiment, description has been givenof an example in which the observation is conducted by use of an SEM;however, the present embodiment is applicable to methods and deviceswhich enable more precise observation as compared with the opticalobservation method, that is, to other electron microscopes including anSTEM, fine machining devices employing a focused ion beam, and analysisdevices using an X-ray analyzer.

Description will be given of another method of calculating the Zposition by referring to FIG. 15. FIG. 15 shows the Z positioncalculating procedure. This method is a method in which images obtainedby an optical microscope are used. First, by use of the Z control unit105, the objective is moved to the lower-most point (a point where theobjective is nearest to the sample; 1101). Next, an image is obtained bythe detector 108 to be transmitted to the control system 10 (1102). Inthis operation, if an edge or a circuit pattern of the sample is in thevisual field, it is favorable to use an image obtained through thebright-field observation; if such pattern is not present and the edge isnot present, it is favorable to use an image obtained through thedark-field observation. After the image is obtained, the objective 104is moved upward for one step by the Z control unit 105 (1103). In thisconnection, the one step is associated with resolution of the Z positiondetection and is favorably equal to or less than half the depth of focusof the objective 104. After the objective 104 is moved, an image isagain obtained. The Z movement and the obtaining of the image arecarried out in a range beforehand set; if the range thus set isexceeded, the obtaining of the image is terminated (1104) and controlgoes to the Z position calculation (1105).

Description will be given of an example of the Z position calculationprocessing. First, a search is made for the maximum luminance point ofeach obtained image, and the luminance and the Z position at which themaximum luminance point is obtained are used to plot a graph (1106).Next, the maximum luminance in the graph 1106 is calculated. In theoperation, it is desirable that the respective measuring points areapproximated to a curved line to calculate the maximum luminance point.The Z point of the calculated maximum luminance point is the positionfor the best focus of the objective 105.

If the Z position calculation described above is employed, the Z sensor7 may be dispensed with; hence, the configuration is simplified.

By referring to FIG. 16, description will be given of a secondconfiguration example of the optical microscope 14 in the presentembodiment. The optical microscope 14 includes a dark-field lightingunit 101, a light introduction mirror 102, a mirror 104, an objective105, a height control unit 106, an imaging optical system 110, asolid-state imaging element 111, an objective rotation unit 117, and aliquid-crystal controller 118. The imaging optical system 110 includesonly an imaging lens 116, and a distribution polarization element 114 isfixed onto a pupil plane 112 a of the objective 105 in theconfiguration.

In this case, the lens system to move the pupil plane 112 a of theobjective 105 to the outside of the objective, the half-silvered mirror108, and the bright-field lighting unit 109 are dispensed with, leadingto an advantage of a simple configuration.

In this situation, to adjust the angle of the distribution polarizationelement 114, there may be disposed a unit 117 which rotates theobjective 105 about the central axis of the objective 105. In theconfiguration, the rotation unit 117 is coupled with the control system10.

By referring to FIG. 17, description will be given of a thirdconfiguration example of the optical microscope 14 in the presentembodiment. The optical microscope 14 includes a dark-field lightingunit 101, a light introduction mirror 102, a mirror 104, an objective105, a height control unit 106, an imaging optical system 110, asolid-state imaging element 111, a liquid-crystal controller 118, and apolarization plate 119. The imaging optical system 110 includes animaging lens 116, and as the distribution polarization element 114, aliquid-crystal element is fixed onto a pupil plane 112 a of theobjective 105 in the configuration. In this configuration, as shown inFIG. 17, the transmission polarization axis of the distributionpolarization element is controllable by a combination of theliquid-crystal controller 118 and a polarization plate 119 which aredisposed outside the objective; this leads to an advantage that bysetting the polarization characteristic of the liquid crystal tonon-polarization, the bright-field observation is enabled, and byproviding the polarization characteristic, highly-sensitive dark-filedobservation is possible. The liquid-crystal controller 118 is coupledwith the controller 10. In this configuration, the objective rotationunit 117 may be advantageously dispensed with. In the configuration, ahalf-silvered mirror 108 and a bright-field lighting unit 109 areemployed to conduct the bright-field observation.

Second Embodiment

Next, description will be given of a second embodiment of the defectinspection device according to the present invention by referring toFIG. 18. The second embodiment differs from the first embodiment in thatthe half-silvered mirror 108 and the bright-field lighting unit 109 arenot arranged. Hence, the configuration is advantageously simplified asshown in FIG. 18. In the configuration shown in FIG. 18, the componentsassigned with the same reference numerals as those of the configurationof FIG. 1 have functions similar to those described by referring to FIG.1.

In this situation, the focusing of the optical microscope 14 is carriedout by use of the Z sensor 7 or through image processing based ondark-field images obtained by the optical microscope 14 as describedabove.

In this case, as in the optical microscope 14 shown in FIG. 16, thedistribution polarization element 114 may be fixed onto the pupil plane112 a of the objective 105 in the configuration.

Third Embodiment

Next, description will be given of a third embodiment of the defectinspection device according to the present invention by referring toFIG. 19. The third embodiment differs from the first embodiment in thatthe Z sensor 7, the half-silvered mirror 108, and the bright-fieldlighting unit 109 are not arranged for the optical microscope 14. Hence,advantageously, the configuration is simplified as shown in FIG. 19 andthere is secured a space in which an objective having a larger numeralaperture is installed as the objective 105. In the configuration shownin FIG. 19, the components assigned with the same reference numerals asthose of the configuration of FIG. 1 have functions similar to thosedescribed by referring to FIG. 1.

In this configuration, the focusing of the optical microscope 14 iscarried out by use of the Z sensor 7 or through image processing basedon dark-field images obtained by the optical microscope 14 as describedabove.

In this occasion, as in the optical microscope 14 shown in FIG. 16, thedistribution polarization element 114 may be fixed onto the pupil plane112 a of the objective 105 in the configuration.

Fourth Embodiment

Next, description will be given of a fourth embodiment of the defectinspection device according to the present invention by referring toFIG. 20. The fourth embodiment differs from the first embodiment in thatthe Z sensor 7 is not arranged for the optical microscope 14. Hence,advantageously, the configuration is simplified as shown in FIG. 20, andthere is secured a space in which an objective having a larger numeralaperture is installed as the objective 105. In the configuration shownin FIG. 20, the components assigned with the same reference numerals asthose of the configuration of FIG. 1 have functions similar to thosedescribed by referring to FIG. 1.

In this case, the focusing of the optical microscope 14 is carried outthrough image processing based on bright-field images or dark-fieldimages obtained by the optical microscope 14 as described above.

In the configuration, as in the optical microscope 14 shown in FIG. 16,the distribution polarization element 114 may be fixed onto the pupilplane 112 a of the objective 105 in the configuration.

Next, by referring to FIGS. 21 to 35, description will be give ofvarious distribution filters 2222 which can be installed in place of thefilter unit 114 used in the respective embodiments above.

Here, as for components of various distribution filters 2222 describedbelow; the arrangement of the phase shifter 391, the inclinations of theslow axis and the fast axis of the wave plates 331 and 332, the opticalrotatory direction by the polarization direction controller 665, and thetransmission polarization axis directions of the light block zone andthe polarization element in the spatial filter are determined based onthe scattered light intensity distribution obtained through thescattered light simulation or through the actual measurement beforehanddescribed by referring to FIG. 9.

Next, description will be given of a method of determining thearrangement of the phase shifter, the inclinations 338 and 339 of theslow axis and the fast axis of the wave plates, and the optical rotatorydirection 780 by the polarization direction controller.

In FIG. 21, (a) and (b) show calculation results of scattered lightsimulation, including the scattered light intensity distribution fN(r,θ)of the scattered light from concavity and convexity on the substratesurface, the distribution pNp(r,θ) of the radial polarization(p-polarized light) component of the scattered light, the distributionpNs(r,θ) of the azimuth polarization (s-polarized light) componentthereof, the distribution pNx(r,θ) of the x polarized light thereof, andthe distribution pNy(r,θ) of the y polarized light thereof as well asthe scattered light intensity distribution fs(r,θ) of the scatteredlight from defects or foreign matter, the distribution psp(r,θ) of theradial polarization (p-polarized light) component of the scatteredlight, the distribution pss(r,θ) of the azimuth polarization(s-polarized light) component thereof, the distribution psx(r,θ) of thex-polarized light thereof, and the distribution psy(r,θ) of they-polarized light thereof. These distributions are obtained through anoperation in which by the scattered light simulation, there are obtainedStokes vectors of the scattered light from fine concavity and convexityon the substrate surface and Stokes vectors of the scattered light fromforeign matter to be detected with high sensitivity and then thedistributions are obtained by use of the Stokes vectors thus obtained.Incidentally, the polarization to be obtained is not limited to thesepolarization, but there may be employed linearly polarized light inwhich the angle of polarization is inclined in a range from π to −π orelliptically (circularly) polarized light.

FIG. 21( a) shows the intensity distribution 771 of the radialpolarization, the intensity distribution 772 of the azimuthpolarization, the intensity distribution 773 of the x polarization, andthe intensity distribution 774 of the y polarization of the scatteredlight (light wavelength 405 nm) from fine concavity and convexity on thesubstrate surface. Further, FIG. 21( b) shows the intensity distribution775 of the radial polarization, the intensity distribution 776 of theazimuth polarization, the intensity distribution 777 of the xpolarization, and the intensity distribution 778 of the y polarizationof the scattered light due to spherical foreign matter having a diameterof 18 nm. Incidentally, the axis 393 indicates an axis on the pupilplane 112 corresponding to the illumination incidence axis.

In each distribution of FIG. 21, a region 779 is a region with highscattered light intensity, a region 780 is a region with slightly highscattered light intensity, a region 781 is a region with slightly lowscattered light intensity, and a region 782 is a region with lowscattered light intensity; however, these areas indicate a relativerelationship with respect to intensity in the distributions, that is,even the same regions in the respective distributions do not necessarilyindicate the same intensity (for example, the intensity distributionregion 779 of the radial polarization and the intensity distributionregion 779 of the x polarization do not necessarily indicate the sameintensity).

According to the scattered light intensity distribution of eachpolarization shown in FIG. 21( a), it is recognizable that the scatteredlight from fine concavity and convexity on the substrate surface isstrong on the illumination incidence 700 side (back scattering), and theradial polarization is strong in the polarization of the backscattering. Also, according to the scattered light intensitydistribution of each polarization shown in FIG. 21( b), it isrecognizable that the scattered light from fine foreign matter issubstantially isotropic, and the radial polarization is strong. Hence,based on these results, by setting and by installing the polarizationfilter according to necessity, it is possible to increase the ratio ofthe scattered light from the substrate surface to that from the foreignmatter, to thereby enable the high S/N defect detection.

FIG. 22 is a diagram showing an example for radial polarization when aphase shifter 391 is employed in the proximity of the pupil plane 112 ofthe optical microscope. Here, as for the polarization direction of thescattered light from the foreign matter, since the vibration directionand the intensity are substantially equal with respect to the axis 393on the pupil plane 112 corresponding to the illumination incidence axis,part of light cancels with each other through interference of lighthaving vibration directions symmetric with respect to the axis 393 onthe pupil plane 112 corresponding to the illumination incidence axis; byusing the phase shifter on the pupil plane 112 and in the vicinity ofthe pupil plane 112, it is possible to mutually strengthen the intensityof the scattered light from the foreign matter. In addition, the phaseshifter may be used to suppress the intensity of the scattered lightfrom the substrate surface or to mutually strengthen the intensity ofthe scattered light from the foreign matter while suppressing theintensity of the scattered light from the substrate surface.

Here, by referring to FIG. 23, description will be more concretely givenof the advantage of the phase shifter according to an example of lightof radial polarization.

According to the result of the scattered light simulation, the scatteredlight from the fine foreign matter is similar to the light of radialpolarization as shown in the radial polarization light distribution 775of FIG. 21( a); the vibration directions oppose to each other in thedirections symmetric with respect to the optical axis; hence, theintensity is lowered due to superimposition. To suppress the lowering ofintensity, the phase shifter is employed for the radial polarization.

FIG. 23( a) shows an application example of radial polarization whereina phase shifter 391 a, which produces a phase difference of π by using,as a boundary, a plane perpendicular to the substrate including the axis393 on the pupil plane 112 corresponding to the illumination incidenceaxis or a plane on the pupil 112 corresponding thereto, is arranged inthe proximity of the pupil plane 112 of the optical microscope. FIG. 23(b) shows an application example of radial polarization wherein a phaseshifter 391 b, which produces a phase difference of π in areas over andunder a boundary in FIG. 23, the boundary being the axis 393 on thepupil plane 112 corresponding to the illumination incidence axis, isarranged in the proximity of the pupil plane 112 of the opticalmicroscope. In FIG. 23( a), it can be considered that the y-directionalcomponents of radial light 392 a and radial light 392 b cancel eachother; hence, when the radial light 392 a interferes with the radiallight 392 b, the peak of the y-directional scattered light intensity islowered. For the scattered light of the radial polarization, when aphase shifter to produce a phase difference of π in areas over and undera boundary in FIG. 23, which is the axis 393 on the pupil plane 112corresponding to the illumination incidence axis, is arranged in theproximity of the pupil plane 112 of the optical microscope; there appearstates 392 c and 392 d in which the y-directional components of 392 cand 392 d strengthen each other; hence, it is possible to heighten thepeak.

In FIG. 23( b), it can be considered that the x-directional componentsof radial polarization light 392 e and radial polarization light 392 fcancel each other; hence, when the radial light 392 e interferes withthe radial light 392 f, the peak of the x-directional scattered lightintensity is lowered. In this situation, when a phase shifter to producea phase difference of π in areas on the left and right sides withrespect to a boundary in FIG. 23, which is an axis 398 perpendicular tothe axis 393 on the pupil plane 112 corresponding to the illuminationincidence axis, is arranged in the proximity of the pupil plane 112 ofthe optical microscope; there appear states 392 g and 392 h in which thex-directional components of 392 g and 392 h strengthen each other;hence, when they interfere with each other, it is possible to heightenthe peak.

Next, description will be given of an example of the distributionpolarization element having an advantage to suppress the scattered lightfrom the substrate surface. As shown in FIG. 21, the scattered lightfrom foreign matter varies in the polarization direction from thescattered light from the substrate surface. By using the polarizationdifference and by installing, on the pupil plane 112 or in the vicinitythereof, a distribution polarization element with zones for each ofwhich the transmission polarization direction is appropriately selected,by use of the scattered light simulation or the actually measuredvalues, to suppress the scattered light from the substrate surface andto minimize the reduction in the scattered light from foreign matter, itis possible to increase the ratio of the scattered light from thesubstrate surface to that from the foreign matter, and it is hencepossible to conduct the high SN defect detection.

As a concrete example, FIG. 24 shows distribution polarization elements742 a, 742 b, 744 a, and 744 b for which the transmission polarizationdirection 9001 (slashes in FIG. 24) is selected, by dividing the spaceon the pupil plane 112 or in the vicinity thereof and by using theresults of the scattered light simulation shown in FIG. 21, for eachdivided area, to thereby suppress the scattered light from the substratesurface and to minimize the reduction in the scattered light fromforeign matter. In this regard, the polarization directions used in thediscussion here include directions of the radial polarization, theazimuth polarization, the x polarization, and the y polarization;however, the present embodiment is not restricted by these directions.

FIG. 24( a) shows examples of distribution polarization elements 742 aand 742 b for which the transmission polarization direction 9001 isselected, by dividing the space 741 on the pupil 112 or in the vicinitythereof into two partitions in the radial direction and in fourpartitions in the circumferential direction, to increase, based on theresults of the scattered light simulation shown in FIG. 21, the ratio ofthe scattered light from the substrate surface to that from the fineforeign matter. For the distribution polarization element 742 a, thetransmission polarization direction 9001 is selected such that theradial polarization light transmits in a zone 951 on the outercircumferential side of the illumination emission side and the ypolarization light transmits in the remaining zone; for the distributionpolarization element 742 b, the transmission polarization direction 9001is selected such that the linear polarization light inclined ±π/4transmits in a zone 951 on the outer circumferential side of theillumination emission side and the y polarization light transmits in theremaining zone.

Further, FIG. 24( b) shows examples of distribution polarizationelements 744 a and 744 b for which the transmission polarizationdirection 9001 is selected by dividing the space 743 on the pupil 112 orin the vicinity thereof into eight partitions in the circumferentialdirection, to increase, based on the results of the scattered lightsimulation shown in FIG. 21, the ratio of the scattered light from thesubstrate surface to that from the fine foreign matter. For thedistribution polarization element 744 a, the transmission polarizationdirection 9001 is selected such that the radial polarization lighttransmits in divided zones 952 a and 952 b and the y polarization lighttransmits in the remaining zone; for the distribution polarizationelement 744 b, the transmission polarization direction 9001 is selectedsuch that the linear polarization light inclined ±π/4 transmits individed zones 952 a and 952 b and the y polarization light transmits inthe remaining zone.

In each of the distribution polarization elements 742 a, 742 b, 744 aand 744 b described above, the scattered light is suppressed, based onthe scattered light simulation results, in the zones in which thescattered light from the substrate surface is strong; hence, it ispossible to conduct the high S/N defect detection. Incidentally, thedistribution polarization elements of FIG. 24 and FIG. 7 described abovemay be used in combination with the phase shifter 391. By using thephase shifter, it is possible to suppress, at occurrence of interferenceamong the scattered light having passed the distribution polarizationelement, the reduction in the intensity taking place due to thesuperimposition. Moreover, although description has been given ofexamples of division into four and eight partitions, the presentembodiment is not restricted by the division; it is only required thatthe area is appropriately divided, according to the scattered lightdistribution, into an appropriate number of partitions to use an optimaldistribution polarization element for each partition; also, in additionto the division in the circumferential direction, the area may beappropriately divided in the longitudinal direction, in the verticaldirection, in the lattice form, and the like. Further, the presentembodiment is not restricted by the use of two kinds of distributionpolarization elements; three or more kinds thereof may be used in theconfiguration.

Next, description will be given of a wave plate which controls thepolarization direction of scattered light from the substrate surface andthat of scattered light from foreign matter to thereby suppress thescattered light from the substrate surface and to suppress the reductionin the intensity of the scattered light from foreign matter. By usingthe wave plate, it is possible to control the polarization direction ofthe scattered light to align the polarization direction, which makes italso possible to simplify the distribution polarization element.

FIG. 25 shows an example of the use of the wave plate in which adistribution ½ wave plate 331 and a distribution ¼ wave plate 332 areemployed in the vicinity of the pupil plane 112 of the opticalmicroscope. Here, as for the distribution ½ wave plate 331 and thedistribution ¼ wave plate 332, the present embodiment is not restrictedby the combination thereof, that is, either one may be employed or thearrangement thereof may be changed according to necessity. Further, itis also possible to use a combination of these wave plates and the phaseshifter 391.

Next, description will be given, in association with an example ofradial polarization, of an advantage when a distribution polarizationelement is employed.

FIG. 26 is a diagram to explain a change in the polarization when a waveplate is employed in the vicinity of the pupil plane 112. By controllingelectric field vectors by the wave plate, it is possible to suppress thescattered light from the substrate and to strengthen the scattered lightfrom foreign matter to be detected, to thereby increase the ratio of thescattered light from foreign matter to the scattered light from thesubstrate surface.

As a concrete example, FIG. 26( a) shows an example of application ofthe ¼ wave plate 332 to elliptic polarization of the polarized light 333a on an arbitrary pupil plane 112. Elliptic polarization light 342 a canbe changed to linear polarization light 342 b by arranging a ¼ waveplate 340 a in which in order that its fast axis 395 matches the majoraxis of elliptic polarization light 342 a inclined by an angle 338relative to the x axis and its slow axis 394 matches the minor of theelliptic polarization light 342 a, the ¼ wave plate is arranged 335 a tobe inclined by an angle 338. By selectively transmitting, by use of thedistribution polarization element, the linear polarization lightobtained by converting the elliptic polarization light, it is possibleto suppress the reduction in the quantity of the scattered light fromforeign matter due to the distribution polarization element.

FIG. 26( b) shows an example of application of the 2/1 wave plate 331 toradial polarization light 334 a on the pupil plane 112. Scattered light775 from the fine foreign matter is similar to the radial polarizationlight; hence, in the directions symmetric with respect to the axis 393on the pupil plane 112 corresponding to the illumination incidence axis,it is likely that the vibration directions of electric field vectorsoppose each other and the intensity is reduced by the superimposition.FIG. 26( b) is an example in which a ½ wave plate 332 is employed tosuppress the reduction in the intensity; for an electric field vector342 c inclined by an angle 337 relative to the axis 393 on the pupilplane 112 corresponding to the illumination incidence axis, by arrangingthe ½ wave plate 332 in the state 341 a as a ½ wave plate 341 b in whichthe fast axis thereof is inclined by an angle of 339, which is half theangle 337, relative to the x axis; the electric field vector 342 c canbe changed to an electric field vector 342 d parallel to the axis 393 onthe pupil plane 112 corresponding to the illumination incidence axis. Inthis way, by arranging the distribution wave plate 332 a on the pupilplane 112 or in the vicinity thereof, the vibration directions of theelectric field vectors become parallel to each other in the directionssymmetric with respect to the axis 393 on the pupil plane 112corresponding to the illumination incidence axis; hence, it is possibleto strengthen the peak intensity of the scattered light through thesuperimposition.

Next, description will be given of an example of arrangement of thepolarization direction controller 665 in which liquid crystal is used inplace of the ½ wave plate 331 and the ¼ wave plate 332 of FIG. 25 byreferring to FIGS. 27 and 28. When liquid crystal is used, it ispossible, by controlling the voltage to be applied thereto and bycontrolling the direction of rubbing on the alignment film, to preciselycontrol the polarization direction, which is not possible by the ½ waveplate 331 and the ¼ wave plate 332 using crystal of quartz.

FIG. 28 is a diagram to explain a change in electric field vectorsaccording to polarization direction control; an electric field vector760 at an arbitrary point 790 and at an arbitrary point of time ischanged to an electric field vector 770 by using the polarizationdirection controller 665. Here, it is assumed that the angulardifference 780 between the electric field vector 760 and the electricfield vector 770 is an optical rotatory angle 780.

FIG. 27( a) shows an example of the optical microscope including apolarization direction controller 665 a configured by appropriatelyusing liquid crystal 663 intercalated between outer-most layers 661 aand 661 b, alignment films 662 and 666, and electrodes 664 a and 664 bin which alignment of molecules of the liquid crystal 663 is controlledby applying a voltage between the electrodes 664 a and 664 b, to therebycontrol the polarization direction.

Here, the liquid crystal is crystal which is in a state between liquidand crystal and which has both of fluidity of liquid and anisotropy ofcrystal; the liquid crystal includes liquid crystal with opticalrotatory power, i.e., having chirality and liquid crystal withoutoptical rotatory power, i.e., not having chirality.

In the liquid crystal having chirality, as exemplified in FIG. 28( b),liquid-crystal molecules 531 a in contact with the substrate rotates andaligns in the perpendicular direction as indicated by 532. The directionof rotation is determined by the chirality of the liquid crystal.

By transmitting light through the liquid crystal 535 a, the polarizationdirection of the light rotates according to the alignment 532 ofmolecules of the liquid crystal, and it is hence possible to change thepolarization state.

When a voltage is applied to the liquid crystal having chirality, thehorizontally arranged molecules of the liquid crystal areperpendicularly arranged as indicated by 531 b; and as molecules of theliquid crystal are further perpendicularly arranged, the opticalrotatory power is lost, that is, liquid crystal 535 b has no opticalrotatory power. The polarization direction can be changed by controllingthe angle of the perpendicular arrangement of the molecules of theliquid crystal according to the magnitude of the applied voltage.

Moreover, in a situation wherein liquid-crystal molecules are in anintermediate state between the state in which the molecules are parallelto the alignment film and the state in which the molecules areperpendicular to the alignment film, if it is likely that the scatteredlight having passed the liquid crystal is not linear polarization lightbut elliptic polarization light, the light which has become the ellipticpolarization light due to the liquid crystal may be changed to thelinear polarization light, by combining the ¼ wave plate. Also, if theoptical rotatory power is not required, for example, in the bright-fieldobservation, the on or off of the optical rotatory power can be easilyselected by applying or not applying a voltage.

FIG. 27( b) is a diagram showing an example of the optical microscopeemploying a polarization direction controller 665 b in which accordingto the rubbing direction or directions of either one or both ofalignment films 662 and 666, alignment of liquid-crystal molecules ofliquid crystal 663 is controlled to thereby control the polarizationdirection. By selecting the rubbing direction, it is possible to createa distribution wave plate capable of precisely implementing a desiredpolarization state. Here, the rubbing direction is the direction,direction of the rubbing process to rub the alignment film using clothwound on a roller; the liquid-crystal molecules have a characteristic toalign in parallel with the rubbing direction.

Next, FIG. 29 shows liquid crystal 663 of a polarization directioncontroller employing liquid crystal having chirality in which theoptical rotatory angle is controllable by use of electrodes. There areemployed a plurality of electrodes which apply a voltage to the liquidcrystal, to thereby control the voltage to be applied to each place ofthe liquid crystal according to desired polarization. In FIG. 29, (a)and (b) show an example employing undivided liquid crystal 663 which hasthe optical rotatory power 396 and which is not divided. When the liquidcrystal 663 is not divided, thickness of liquid crystal 663 isdetermined to obtain an optical rotatory angle in a range from 2π to 0or a range from 0 to −2π.

As for an example of voltages to be applied to the liquid crystal,scattered light 775 from fine foreign matter is similar to the radialpolarization light; hence, in the directions symmetric with respect tothe axis 393 on the pupil plane 112 corresponding to the illuminationincidence axis, the vibration directions of electric field vectorsoppose to each other and the reduction in the intensity may take placedue to the superimposition; therefore, in order to obtain a polarizationdirection to suppress the peak intensity reduction of the scatteredlight from foreign matter by aligning directions of electric fieldvectors, different voltages are applied to the respective electrodes.Or, the voltages of the respective electrodes are controlled to obtain apolarization direction to weaken scattered light from the samplesurface. As a result, it is possible to increase the ratio of the peakintensity of the scattered light from the sample surface to that of thescattered light from the foreign matter.

In addition, it is also possible that by dividing the liquid crystal 663into several partitions such that a voltage is applied to each of thepartitions of the liquid crystal to control the direction of theliquid-crystal molecules of the liquid crystal, to thereby control theoptical rotatory direction. FIG. 29( c) shows an example in which theliquid crystal is divided into two partitions with respect to an angle.It is only necessary in FIG. 29( c) that the controllable opticalrotatory angles of the two partitions 663 b and 663 c of the liquidcrystal are respectively in a range from π to 0 and a range from 0 to−π. FIG. 29( d) shows an example in which the liquid crystal 633 isdivided into four partitions with respect to an angle. According to thenumber of partitions, the maximum controllable optical rotatory angleand the combination of the liquid crystal 633 are determined. Throughthe division, it is possible to control each divided area; hence, theoptical rotatory angle can be more precisely controlled as a whole.Incidentally, the embodiment is not restricted by the number ofpartitions and the dividing method; they may be set according tonecessity.

Further, the liquid crystal 633 is not limited to one layer, but aplurality of layers may be used. When a plurality of layers areemployed, a voltage may be applied to each layer or may be applied tothe plural layers at the same time. In FIG. 29; (e), (f), and (g) showan example in which the liquid crystal is divided into two partitionswith respect to an angle and which includes two layers of liquidcrystal. FIG. 29 (e) shows the dividing method. FIG. 29 (e) shows theupper-layer liquid crystal and FIG. 29 (f) shows the lower-layer liquidcrystal. In this example, for the upper-layer liquid crystal 663 i and663 h, liquid crystal having the plus-directional optical rotatory power396 d is employed; for the lower-layer liquid crystal 663 k and 663 j,liquid crystal having the minus-directional optical rotatory power 396 eis employed. It is possible that both of the upper and lower layers aredivided into two partitions with respect to the axis 393 on the pupilplane 112 corresponding to the illumination incidence axis and differentvoltages are respectively applied to the liquid crystal 663 i, 663 h,663 k, and 663 j. For example, when it is desired to obtain theplus-directional optical rotatory power on the upper side of FIG. 29 (c)with respect to the axis 393 on the pupil plane 112 corresponding to theillumination incidence axis and the minus-directional optical rotatorypower on the lower side of FIG. 29 (c) with respect to the axis 393 onthe pupil plane 112 corresponding to the illumination incidence axis, itis only required that a voltage is applied to the liquid crystal 663 iand 663 j and no voltage is applied to the liquid crystal 663 h and 663k. By piling up a plurality of layers of liquid crystal, the opticalrotatory angle can be more precisely controlled.

Here, the liquid crystal 663 of the polarization controller of FIG. 27(a) is crystal having the optical rotatory power; hence, as for thealignment films 662 and 666 of the polarization controller of FIG. 27(a), an alignment film without rubbing is used for both thereof or foreither one thereof.

FIG. 30 shows an example in which the radial polarization light ischanged to the x polarization light by use of a polarization controllerincluding liquid crystal which does not have the optical rotatory power396 and which has width adjusted to obtain the function of the ¼ waveplate. The scattered light from fine foreign matter is similar to theradial polarization light; hence, in the directions symmetric withrespect to the axis 393 on the pupil plane 112 corresponding to theillumination incidence axis, the vibration directions of electric fieldsoppose each other and the intensity is reduced by the superimposition;to suppress the intensity reduction, there is employed the liquidcrystal not having the optical rotatory power 396.

In this polarization controller, when no voltage is applied to theliquid crystal 663 m, the optical rotatory direction can be changed fromthe radial polarization to the x polarization; on the other hand,although the optical rotatory direction can be changed when a voltage isapplied thereto, if the voltage exceeds a threshold value, the opticalrotatory power is lost. Here, the rubbing is conducted on the loweralignment film 666 b to obtain the desired optical rotatory angle, andthe rubbing is not conducted on the upper alignment film 666 b for theoperation.

Next, description will be given, by using FIG. 31 as an example, of apolarization controller employing liquid crystal to which no voltage isapplied and for which the rubbing direction on the alignment film isselected for a desired optical rotatory angle. In the liquid crystal nothaving the chirality, the molecules of the liquid crystal align in therubbing direction of the lower alignment film 666. FIG. 31( a) showsalignment of the liquid-crystal molecules when the rubbing direction ofthe lower alignment film differs from that of the upper alignment filmby π/2. The liquid-crystal molecules align along the alignment film, andan optical rotatory angle of π/2 is obtained for the alignment filmarrangement of FIG. 31( a).

Hence, as for the polarization controller which operates by selectingthe rubbing direction of the lower alignment film 662 and that of theupper alignment film 666, it is possible to implement a more precisepolarization controller to control polarization more precisely whencompared with the controller employing the distribution ½ wave plate.

FIG. 31 is a diagram showing an example of the polarization directioncontroller in which the rubbing directions of the alignment films 662 aand 666 c are adjusted for the desired polarization directions. In FIG.31, (c) and (d) as well as (e) and (f) respectively show the alignmentfilm rubbing directions when the radial polarization light shown in FIG.31( b) is changed into the x polarization light (FIG. 31( g)) and intothe y polarization light (FIG. 31( h)). Description will be given ofcontrol of the polarization direction according to the rubbing directionby referring to FIG. 31( c). There is shown an example of thepolarization controller employing liquid crystal not having the opticalrotatory power to suppress an event in which since the scattered lightfrom fine foreign matter is similar to the radial polarization light,the vibration directions of electric field vectors oppose each other inthe directions symmetric with respect to the axis 393 on the pupil plane112 corresponding to the illumination incidence axis and the intensityis reduced by the superimposition.

The rubbing directions of the alignment films 662 a and 662 b aredetermined such that the difference between the inclinations of therubbing directions of the alignment films 662 a and 662 b at arbitrarypoints on the pupil plane 112 or in the neighborhood thereof is equal tothe desired optical rotatory angle.

An electric field vector 342 c at a point 1601 a and at an arbitrarypoint of time is changed to an electric field vector 342 e by use of thepolarization direction controller 665 b. At the point 1601, the rubbingdirection angular difference between the alignment films 662 a and 662 bis π/4. Hence, the electric field vector 342 c changes in thepolarization direction by π/4, and there is obtained the linearpolarization light 342 e of the x polarization.

Next, description will be given of a polarization controller employing amagnetooptical effect.

FIG. 32 shows an example of arrangement of a polarization directioncontroller in which a transparent magnetic substance using amagnetooptical effect is employed in place of the ½ wave plate 331 andthe ¼ wave plate 332 of FIG. 25. In this example, by controlling thepolarization direction of the transparent magnetic substance 668intercalated between transparent substrates 667 and 669, thepolarization direction is controlled by use of the Faraday rotation.

Further, FIG. 33 shows an example of use of a transparent magneticsubstance symmetrically divided with respect to the axis 393 on thepupil plane 112 corresponding to the illumination incidence axis.Through an operation in which the transparent magnetic substances 668 aand 668 b symmetrically arranged with respect to the axis 393 on thepupil plane 112 corresponding to the illumination incidence axis aremagnetized in the symmetric directions, there can be obtained an opticalrotatory angle 780 symmetric with respect to the axis 393 on the pupilplane 112 corresponding to the illumination incidence axis. In thedirections symmetric with respect to the axis 393 on the pupil plane 112corresponding to the illumination incidence axis, the vibrationdirections of electric field vectors oppose each other, and when thescattered light is superimposed, the intensity of the y polarizationlight of the scattered light from the defect is reduced; however, thereduction in the peak intensity of the scattered light can be suppressedby selecting, by use of the polarization direction controller employingthe magnetooptical effect, the direction of magnetization to align thedirections of magnetic field vectors in one direction. Incidentally, thedirection of magnetization is not necessarily parallel to the pupilplane 112. Also, the number of divisions of the transparent magneticsubstance may be one or more. Further, the number of layers of thetransparent magnetic substance is not limited to one; a plurality oflayers may be piled up.

In addition, the direction of magnetization is controlled by applying anexternal magnetic field, by applying stress onto the crystal using apiezoelectric actuator or the like, by applying an electric field, or byapplying an external magnetic field and by applying stress onto thecrystal using a piezoelectric actuator or the like. Incidentally, whenthe optical rotatory power is not required in the bright-fieldobservation or the like, the optical rotatory power can be easilyremoved by not applying the stress, by not applying the electric field,or by not applying the external magnetic field.

Here, as the spatial filter described above, there may be employed adistribution filter implemented by combining a polarization element witha light block plate in which the ratio between the foreign matterscattered light quantity and the substrate surface scattered lightquantity is derived through scattered light simulation or actualmeasurement such that an area with the ratio more than a threshold valuetransmits light and an area with the ratio between the foreign matterscattered light and the substrate surface scattered light less than athreshold value blocks light. By removing the area having a small ratiobetween the foreign matter scattered light and the substrate surfacescattered light, it is possible to increase the ratio between theforeign matter scattered light quantity and the substrate surfacescattered light quantity in the overall pupil plane 112.

FIG. 34 shows an example of the distribution filter including acombination of a polarization element and a light block plate.

Here, discussion has been given on a combination of a polarizationelement and a light block plate in which the ratio between the foreignmatter scattered light quantity and the substrate surface scatteredlight quantity is derived for each of radial polarization light, azimuthpolarization light, x polarization light, and y polarization light suchthat an area with an arbitrary ratio more than a threshold valuetransmits light and an area with the ratio between the foreign matterscattered light and the substrate surface scattered light less than anarbitrary threshold value blocks light. Also, in a situation in whichthe ratio between the foreign matter scattered light quantity and thesubstrate surface scattered light quantity is more than an arbitrarythreshold value for both of the x polarization light and the ypolarization light, the polarization element and the light block plateare not employed.

A distribution spatial filter 881 a obtained according to the results ofthe scattered light simulation used to draw FIG. 21 includes acombination of areas 886 a and 886 b with no polarization element and nolight block plate, light block plates 885 a and 885 b, a polarizationelement 887 a having a transmission polarization axis inclined 2/πrelative to the x polarization light, a polarization element 887 bhaving a transmission polarization axis inclined 2/π relative to the xpolarization light, and polarization elements 888 a and 888 b includingtransmission polarization elements to transmit x polarization light.

Moreover, a distribution filter 881 b as another distribution spatialfilter is an example of the distribution filter obtained as a result ofdiscussion on the combination of a polarization element and a lightblock plate in which the ratio between the foreign matter scatteredlight quantity and the substrate surface scattered light quantity isderived for radial polarization light based on the results of thescattered light simulation used to draw FIG. 21 such that an area withan arbitrary ratio more than a threshold value transmits light and anarea with the ratio between the foreign matter scattered light and thesubstrate surface scattered light less than an arbitrary threshold valueblocks light; and the filter includes a combination of light blockplates 885 c and 885 d, a polarization element 887 c having atransmission polarization axis inclined 2/π relative to the xpolarization light, and a polarization element 887 d having atransmission polarization axis inclined 2/π relative to the xpolarization light.

Here, when a polarization element having a transmission polarizationaxis which radially extends (in the radial direction) is employed forthe polarization elements 887 a and 887 c having a transmissionpolarization axis inclined π/2 relative to the x polarization light andthe polarization elements 887 b and 887 d having a transmissionpolarization axis inclined π/2 relative to the x polarization light, theratio of the scattered light quantity from the defect to that from thesample surface is improved.

A distribution filter 881 c is an example of the distribution filterobtained as a result of discussion on the combination of a polarizationelement and a light block plate in which the ratio between the foreignmatter scattered light quantity and the substrate surface scatteredlight quantity is derived for x polarization light based on the resultsof the scattered light simulation used to draw FIG. 21 such that an areawith an arbitrary ratio more than a threshold value transmits light andan area with the ratio between the foreign matter scattered light andthe substrate surface scattered light less than an arbitrary thresholdvalue blocks light; and the filter includes a combination of a lightblock plate 885 e and a polarization element 888 c having a transmissionpolarization element to transmit x polarization light.

A distribution filter 881 d is an example of the distribution filterobtained as a result of discussion on the combination of a polarizationelement and a light block plate in which the ratio between the foreignmatter scattered light quantity and the substrate surface scatteredlight quantity is derived for y polarization light based on the resultsof the scattered light simulation used to draw FIG. 21 such that an areawith an arbitrary ratio more than a threshold value transmits light andan area with the ratio between the foreign matter scattered light andthe substrate surface scattered light less than an arbitrary thresholdvalue blocks light; and the filter includes a combination of a lightblock plate 885 f and polarization elements 889 a and 889 b having atransmission polarization element to transmit y polarization light.Incidentally, this embodiment is not restricted by these combinations ofthe polarization element and the light block plate, but any appropriatecombination may be selected according to the scattered lightdistribution.

As a result of discussion on the combination of a polarization elementand a light block plate in which the ratio between the foreign matterscattered light quantity and the substrate surface scattered lightquantity is derived for azimuth polarization light based on the resultsof the scattered light simulation used to draw FIG. 21 such that an areawith an arbitrary ratio more than a threshold value transmits light andan area with the ratio between the foreign matter scattered light andthe substrate surface scattered light less than an arbitrary thresholdvalue blocks light, there have not been any coordinates on the pupilplane 112 where the threshold value is exceeded.

Next, description will be given of a distribution filter including acombination of a polarization element and a light block plate in whichthe pupil plane 112 or the pupil plane 112 is divided into arbitraryareas. By dividing the pupil plane 112 or the pupil plane 112 intoarbitrary areas, there is obtained more feasibility when compared withthe distribution filter of FIG. 34.

FIG. 35 shows an example of a distribution filter including acombination of a polarization element and a light block plate in whichthe ratio between the foreign matter scattered light quantity and thesubstrate surface scattered light quantity is derived for radialpolarization light, azimuth polarization light, x polarization light,and y polarization light for each of the arbitrary areas on the pupilplane 112 or the pupil plane 112 through scattered light simulation oractual measurement such that an area with the ratio more than athreshold value transmits light and an area with the ratio between theforeign matter scattered light and the substrate surface scattered lightless than a threshold value blocks light.

Here, discussion has been given on a combination of a polarizationelement and a light block plate in which the ratio between the foreignmatter scattered light quantity and the substrate surface scatteredlight quantity is derived for each of radial polarization light, azimuthpolarization light, x polarization light, and y polarization light suchthat an area with an arbitrary ratio more than a threshold valuetransmits light and an area with the ratio between the foreign matterscattered light and the substrate surface scattered light less than anarbitrary threshold value blocks light. Further, in a situation in whichthe ratio between the foreign matter scattered light quantity and thesubstrate surface scattered light quantity is more than an arbitrarythreshold value for both of the x polarization light and the ypolarization light, the polarization element and the light block plateare not employed.

Distribution filters 890 a and 890 b are examples in which the pupilplane 112 is divided into eight areas in the radial direction such thatthe filters are implemented by appropriately combining a polarizationelement and a light block plate of radial polarization light, azimuthpolarization light, x polarization light, or y polarization light foreach of the eight divided areas. Moreover, distribution filters 890 c to890 f are examples in which the pupil plane 112 is divided into eightareas in the radial direction and into two areas in the circumferentialdirection such that the filters are implemented by appropriatelycombining a polarization element and a light block plate of radialpolarization light, azimuth polarization light, x polarization light, ory polarization light for each of the 16 divided areas.

In this regard, in the distribution filters, it is possible to controlthe polarization direction by a wave plate and to select polarization bya polarization plate. By combining the wave plate with the polarizationelement, it is possible to simplify the transmission polarization axisdirection of the polarization element employed to increase the ratiobetween the scattered light quantity from foreign matter and thescattered light quantity from the substrate surface. For example, inareas 887 e and 887 f of the distribution filter 890 a to transmit lightof radial polarization, by placing a distribution ½ wave plate toconvert the vibration direction of the electric field from the radialpolarization into the y polarization, there may be used a distributionfilter including a combination of a ½ wave plate, a polarization elementfor y polarization, and a light block plate.

Also, it is possible to employ, in place of the ½ wave plate of thedistribution filter, a polarization direction controller using liquidcrystal or a polarization direction controller including a transparentsubstance using the magnetooptical effect described above. In thissituation, the polarization direction can be controlled more preciselywhen compared with the ½ wave plate. In addition, the on or off of theoptical rotatory power can be easily selected. Further, it is alsopossible that a phase shifter is combined with the distribution filterincluding the combination of a wave plate, a polarization element, and alight block plate. By combining the phase shifter with the distributionfilter, when the scattered light having passed the distribution filterinterferes with each other, it is possible that the reduction in theintensity due to the superimposition is suppressed and the peakintensity is strengthened by the superimposition. Or, photonic crystalhaving a function of a phase shifter, a polarization element, a lightblock plate, a wave plate, or a combination thereof may be employed asthe distribution filter. By using the photonic crystal, it is possibleto implement a distribution filter having precise polarizationselectivity and a precise polarization direction control function.

Due to reduction in size of the foreign matter to be detected, due toutilization of the spatial filter 114, or due to both thereof, theintensity of the scattered light from the foreign matter is lowered;hence, a highly sensitive sensor 111 may be employed to multiply verylow intensity of the scattered light from fine foreign matter or tosuppress noise caused by the sensor 111. By using the highly sensitivesensor 111, it is possible to increase the ratio of the scattered lightfrom the defect to the noise caused by the sensor. For example, for thehighly sensitive sensor 111, it is only necessary to appropriatelyemploy a Cooled CCD camera, an Intensified CCD camera (ICCD camera), aSilicon Intensified CCD camera (SIT camera), an Electron Bombardment CCDcamera (EB-CCD camera), or an Electron Multiplier CCD camera (EM-CCDcamera).

The various distribution filters described above may be employed as asingle unit or in combination with each other according to necessity,and are applicable to the inspection devices of the respectiveembodiments described above as well as to the inspection devices ofrespective embodiments, which will be described later.

Fifth Embodiment

Description will be given of a defect observation device in a fifthembodiment according to the present invention by referring to FIG. 36.As for FIG. 36, the electron microscope 5 and the like are omitted andonly a defect detection device will be described. An inspection deviceto inspect a surface of or a defect on an inspection target sample 557includes, according to necessity, a illumination optical systemincluding a laser 551, an expander 552, an attenuator 553, apolarization control element 554, mirrors 555A and 555B, and a lens 556;a stage including a Z stage 558 and an XY stage 559; a sample heightmeasurement unit 560; a detection optical system including, according tonecessity, an objective 561, a spatial filter 562, an imaging lens 563,and a sensor 564; a signal processing unit 565, and a monitor 567. Inaddition, the inspection device includes, according to necessity, adetection system monitoring unit 571 which includes a half-silveredmirror 569 and a sensor 570 and which measures a state of the detectionoptical system; further, although not shown, a illumination systemmonitoring unit to measure a state of the illumination optical systemand a control unit 800 to control respective associated units, whichwill be described later.

First, description will be given of the configuration of theillumination optical system. The laser 551 emits illumination light 568in a direction inclined with respect to the direction of the normal ofthe inspection target sample, to form a desired beam of a spot, a linearform, or the like on a surface of the inspection target sample 557. Theexpander 552 expands the illumination light 568 to a parallel flux oflight according to a fixed magnification factor. The attenuator 553 isan attenuator to control the quantity and intensity of illuminationlight 568 having passed the expander 552. The polarization controlelement 554 is an element which changes the direction of molecules ofliquid crystal by rotating a polarization plate or a wave plate or byconducting voltage on and off control to change the polarizationdirection of light incident to the element, to thereby control thepolarization state. The mirrors 555A and 555B are a group of reflectionmirrors employed, when the illumination light 568 after the polarizationcontrol (control of the electric field phase and amplitude) is emittedonto the inspection target sample 557, to adjust the lighting angle.Here, although two mirrors are used in this example, it is also possiblethat no mirror is employed in the configuration; or, one mirror or threeor more mirrors may be used in the configuration. The lens 556 is a lensto focus the illumination light 568 onto a radiation positionimmediately before the light is emitted onto the inspection targetsample 557.

Next, description will be given of the configuration of the detectionoptical system. The objective 561 is an objective lens which focuses, inthe direction of the normal (from above) of the inspection target sample557, light scattered or light diffracted by foreign matter, a defect, ora pattern on the inspection target sample 557 due to radiation of theillumination light 568 from the laser 551. In this situation, when theinspection target sample 557 such as a semiconductor device to beinspected by this dark-field defect inspection device includes arepetitive pattern, diffracted light caused by the repetitive pattern isfocused with a regular interval onto the emission pupil of the objective561. The spatial filter 562 is a filter to block light of the repetitivepattern in the vicinity of the pupil plane 112 or a filter to controland to select the polarization direction for all of, part of, or lightof a particular polarization of the light reflected by the inspectiontarget sample. The imaging lens 563 is a lens to focus light which isscattered or diffracted by other than the repetitive pattern (forexample, a position of occurrence of failure) and which has passed thespatial filter 562, to thereby form an image on the sensor 564. Thesensor 564 is an optical sensor to transmit the image focused andproduced by the imaging lens 563 as electronic information to the signalprocessing unit 565. The kinds of the optical sensors are CCD and CMOSin general; however, here, any kind thereof is available.

The signal processing unit 555 includes a circuit to convert image datareceived from the sensor 564 into a state which can be displayed on themonitor 567.

The XY stage 559 is a stage to place thereon the inspection targetsample 557; by moving the XY stage 559 in the direction of a plane, theinspection target sample 557 is scanned. Further, the Z stage 558 is astage to perpendicularly (in the z direction) move an inspectionreference plane (a plane on which the inspection target sample 557 isplaced) of the XY stage 559.

The sample height measurement unit 560 is a measuring unit to measurethe inspection reference plane of the XY stage 559 and the height of theinspection target sample 557. By use of the Z stage 558 and the sampleheight measurement unit 560, it is possible to provide an automaticfocus function to automatically conduct the focusing operation.

Next, description will be given of overall operation of this inspectiondevice.

First, the illumination light 568 from the laser 551 is emitted onto asurface of the inspection target sample 557 in a direction inclined withrespect to the direction of the normal of the inspection target sample,to form a desired beam on the inspection target sample 557. Lightscattered or light diffracted by foreign matter, a defect, or a patternon the inspection target sample 557 due to the beam is focused by theobject 561 over the inspection target sample. When the inspection targetsample 557 includes a repetitive pattern, diffracted light caused by therepetitive pattern is focused with a regular interval onto the emissionpupil of the objective, and is hence blocked by the spatial filter 562placed on the pupil plane 112. On the other hand, light scattered ordiffracted by other than the repetitive pattern passes the spatialfilter 562 and is fed to the imaging lens 563, to thereby form an imageon the sensor 564.

The inspection target sample 557 is placed on the XY stage 559 and isscanned by use of the XY stage 559, to thereby obtain a two-dimensionalimage of the scattered light from the inspection target sample 557. Inthe operation, the distance between the inspection target sample 557 andthe objective 561 is measured by the sample height measurement unit 560and is then adjusted by the Z stage 558.

The two-dimensional image obtained by the sensor 564 is classified bythe signal processing unit 565 according to the foreign matter kind andthe defect kind such that the size of the foreign matter or the defectis obtained, and the result is displayed on the monitor 567.

Here, FIG. 37 shows an example of the contour of the spatial filter 562arranged in the proximity of the pupil plane 112 to remove the scatteredlight caused by the pattern. As for the example of each spatial filtershown in FIG. 37, the filter is arranged on the pupil plane 112 or inthe proximity thereof and a dark area indicates a light block zone andan open area indicates a light flux transmission zone. This diagramshows an example in which nine small openings are disposed in thecentral area (562 a), an example in which a large opening is disposed inthe central area (562 b), an example in which a middle-sized opening isdisposed in the central area (562 c), and an example in which two smallopenings are disposed in the central area (562 d); however, theembodiment is not restricted by these examples; the openings may bedisposed in the form of perpendicular or longitudinal stripes, and thenumber and the size of openings may be set according to necessity.Incidentally, the image on the pupil plane 112 represents angularcomponents of diffracted or scattered light of the inspection targetsample; hence, by determining positions and sizes of openings to bedisposed, it is possible to select the diffracted or scattered light ofthe inspection target sample. In addition, it is also possible thatvarious distribution filters 2222 are used in combination with thespatial filter 562 according to necessity, and these distributionfilters 2222 may be employed in place of the spatial filter 562.

Next, description will be given of the control unit 800 according to thefifth embodiment of the present invention by referring to FIG. 38. FIG.38 is a block diagram showing an internal configuration of the controlunit 800; the control unit 800 includes, according to necessity, arecording unit 801, a comparing unit 802, a sensitivity predicting unit803, and a feedback control unit 804.

The recording unit 801 receives inputs of data items from theillumination system monitoring unit and the detection system monitoringunit 571 which have conducted monitoring operations, and records thesedata items. The comparing unit 802 receives inputs of data recorded inthe recording unit 801 and compares the data with an ideal value in adatabase 805. Incidentally, before the processing in the comparing unit802, characteristics of the light source and elements in the monitoringoperation are beforehand calculated. The sensitivity predicting unit 803estimates and predicts the present device sensitivity based on thedifference between the record data and the ideal value. If thedifference between the record data and the ideal value is in anallowable range, respective associated units of the illumination opticalsystem and the detection optical system are controlled to startinspection. If the difference is beyond the allowable range, thefeedback control unit 804 performs a feedback control operation for therespective associated units of the device according to the predictedsensitivity predicted by the sensitivity predicting unit 803.

In this regard, the database 805 is a database of ideal values to beused by the comparing unit 802; to this database 805, ideal values arebeforehand inputted through logical calculations, optical simulation,and the like. In the operation, the inspection target sample is modeledin an optical simulator to derive the intensity of scattered light andthe like from the inspection target sample taking place depending onconditions of the illumination optical system, to calculate intensity oflight detected by a detector. The parameters of ideal values in thedatabase 805 include information pieces of the intensity distribution,the polarization state distribution, the focal distance of the imaginglens 563, and the sensitivity of the sensor 564 of the illuminationoptical system. It is required to beforehand obtain characteristics ofthese parameters.

Next, by referring to the flowchart of FIG. 39, description will beconcretely given of a monitoring processing procedure in the dark-fielddefect detection device according to the fifth embodiment of the presentinvention.

First, the lighting-system monitoring unit monitors the state of theillumination system (step S10). Further, the detection-system monitoringunit 571 measures the state of the detection system (step S11).Measurement results obtained in steps S10 and S11 are sent to thecomparing unit 802. The comparing unit 802 compares these measurementresults with ideal values in the database 805 to further predict thedetection sensitivity based on “difference” between the ideal values andthese measurement results (step S12). The comparing unit 802 then judgesif the predicted detection sensitivity is larger or smaller than athreshold value arbitrarily set (step S13).

If the predicted sensitivity is equal to or less than the thresholdvalue, the optical system is calibrated (step S14), and then controlreturns again to step S10. In this connection, if all positionsrequiring calibration can be automatically controlled, it is alsopossible to automatically carry out all operations of calibration. Inthis operation, it is only required that the calibration positions arebeforehand determined through a logical calculation or optical-systemsimulation. On the other hand, if the predicted sensitivity is equal toor more than the threshold value, inspection is started for theillumination system and the detection system (step S15).

As above, the invention devised by the present inventor has beenspecifically described based on embodiments; however, the presentinvention is not restricted by the embodiments above, and it is to beappreciated that various changes are possible without departing from thegist of the present invent.

REFERENCE SIGNS LIST

-   1 . . . Sample 2 . . . Sample holder 3 . . . Stage 4 . . . Optical    height detection device 5 . . . Electron microscope 6 . . . Vacuum    chamber 7 . . . Optical height detection device 10 . . . Control    system 11 . . . User interface 14 . . . Optical microscope 101 . . .    Dark-field lighting unit 102 . . . Light introduction mirror 104 . .    . Mirror 105 . . . Objective 106 . . . Height control unit 108 . . .    Half-silvered mirror 109 . . . Bright-field illumination 110 . . .    Imaging optical system 111 . . . Solid-state imaging element 113 . .    . Lens group 114 . . . Distribution polarization element 116 . . .    Imaging lens 117 . . . Objective rotation unit 118 . . .    Liquid-crystal controller 111 . . . Polarization plate 501 . . .    Illumination light source 502 . . . Optical filter 503 . . . Wave    plate 507 . . . Lens group 751 . . . Light source 702 . . . Focusing    lens 703 . . . Slit 704 . . . Projection lens 705 . . . Light    reception lens 706 . . . Detector 401 . . . Filter changeover unit    402 . . . Holder 405 . . . Distribution polarization element holder    2222 . . . Distribution filter 391 . . . Phase shifter 742, 744 . .    . Area-division-type distribution polarization element 331 . . .    Distribution ½ wave plate 332 . . . Distribution ¼ wave plate 665 .    . . Polarization direction controller employing liquid crystal 670 .    . . Polarization direction controller employing transparent magnetic    substance

1. A defect detection device, comprising: a illumination optical systemfor emitting laser onto a surface of an inspection target object in aninclined direction; and a detection optical system for focusing, by anobjective lens, scattered light from the inspection target object due tothe laser emitted as above, to thereby form an image on a solid-stateimaging element, wherein the detection optical system comprises adistribution filter for controlling a polarization direction ofscattered light, included in the scattered light from roughness of theinspection target surface and a polarization direction of scatteredlight, included in the scattered light from foreign matter or a defecton the inspection target object surface and for selecting a polarizationdirection of light to be transmitted.
 2. The defect detection deviceaccording to claim 1, wherein the distribution filter includes a waveplate, a spatial filter, a polarization element, or any combination ofthe wave plate, the spatial filter and the polarization element.
 3. Thedefect detection device according to claim 1, wherein the distributionfilter is a wave plate having a distribution of fast axis direction andslow axis direction to control the polarization direction of thescattered light due to the roughness of the inspection target surfaceand the polarization direction of the scattered light due to foreignmatter or a defect on the inspection target object surface.
 4. Thedefect detection device according to claim 1, wherein the distributionfilter includes a combination of a wave plate and a linear polarizationelement for aligning the polarization directions to increase a ratio ofthe scattered light due to foreign matter or a defect on the inspectiontarget object surface to the scattered light due to the roughness of theinspection target surface.
 5. The defect detection device according toclaim 1, wherein the distribution filter includes a combination of awave plate and a distribution polarization element for aligning thepolarization directions to increase a ratio of the scattered light dueto foreign matter or a defect on the inspection target object surface tothe scattered light due to the roughness of the inspection targetsurface.
 6. The defect detection device according to claim 1, whereinthe distribution filter is a wave plate including either one selectedfrom a ½ wave plate, a ¼ wave plate, a combination of a ½ wave plate anda ¼ wave plate, liquid crystal, a magnetooptical modulation element,photonic crystal, a combination of a ¼ wave plate and liquid crystal,and a combination of a ¼ wave plate and a magnetooptical modulationelement.
 7. The defect detection device according to claim 1, whereinthe distribution filter is a spatial filter comprising a scattered lightblock unit including either one selected from a combination of a linearpolarization element and a magnetooptical modulation element, acombination of a linear polarization element and a wave plate, acombination of a polarization element and a magnetooptical modulationelement, and a combination of a polarization element and a wave plate.8. The defect detection device according to claim 1, wherein thedistribution filter is a polarization element comprising a polarizedlight transmission axis to selectively transmit polarized light having ahigh ratio of the scattered light due to foreign matter or a defect onthe inspection target object surface to the scattered light due toroughness of the inspection target surface.
 9. The defect detectiondevice according to claim 1, wherein the distribution filter is a phaseshifter for changing a phase of scattered light to increase a ratio ofthe scattered light due to foreign matter or a defect on the inspectiontarget object surface to the scattered light due to the roughness of theinspection target surface.
 10. The defect detection device according toclaim 1, wherein at least one of the distribution filters is arranged ona pupil plane or in the vicinity of the pupil plane of the detectionoptical system or between the objective lens and the detection targetobject.
 11. The defect detection device according to claim 1, wherein atleast one of the distribution filters includes a changeable mechanism.12. The defect detection device according to claim 1, wherein at leastone of the distribution filters is buried in the objective lens.
 13. Thedefect detection device according to claim 1, further comprising adistribution filter including a liquid crystal or a magnetoopticalmodulation element in a pupil plane of the detection optical system anda control mechanism capable of changing a direction distribution of apolarized light transmission axis.
 14. The defect detection deviceaccording to claim 1, wherein when the inspection target object is amirror surface, p-polarized light is emitted onto the inspection targetobject with an elevation angle of about 10°.
 15. The defect detectiondevice according to claim 1, wherein the laser employed in theillumination optical system is either one selected from visible laser,ultraviolet laser, and vacuum ultraviolet laser.
 16. The defectdetection device according to claim 1, further comprising an opticalheight sensor for obtaining height information required to focus theobjective lens.
 17. A defect observation device, comprising: a defectdetection device comprising a illumination optical system for emittinglaser onto a surface of an inspection target object in an inclineddirection and a detection optical system for focusing, by an objectivelens, scattered light from the inspection target object due to the laseremitted as above, to thereby form an image on a solid-state imagingelement; and an electron microscope for conducting positioning based onpositional information, obtained by the defect detection device, of adefect or foreign matter on the inspection target object surface and forobserving the defect or the foreign matter, wherein the detectionoptical system of the defect detection device comprising a distributionfilter for controlling a polarization direction of scattered light,included in the scattered light from roughness of the inspection targetsurface and a polarization direction of scattered light, included in thescattered light from foreign matter or a defect on the inspection targetobject surface and for selecting a polarization direction of light to betransmitted.
 18. The defect observation device according to claim 17,wherein the distribution filter is a distribution polarization element,a space filter, or a polarization element having a configuration toremove the scattered light from the roughness of the inspection targetsurface and to selectively transmit the scattered light from the foreignmatter or a defect on the inspection target object surface.
 19. Thedefect observation device according to claim 17, wherein thedistribution filter is either one selected from a wave plate, acombination of a wave plate and a polarization element, and acombination of a wave plate, a polarization element, and a spatialfilter.
 20. The defect observation device according to claim 17, whereinthe distribution filter is either one selected from a distribution waveplate, a combination of a distribution wave plate and a polarizationelement, and a combination of a distribution wave plate, a polarizationelement, and a spatial filter.
 21. (canceled)
 22. (canceled) 23.(canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)
 27. (canceled)28. (canceled)